Ishopanishad has the Message of Karmayog

The life of humans is considered to be the best of all the living beings because rest of other living beings are are born in the form of consumers and materialistic but the life of human beings and their actions are are such in which we have Karma or action as the primary force. Therefore The Almighty has given us body mind wisdom prosperous soul and the knowledge of Vedas because the action according to the teachings of Vedas and scriptures is considered to be the best action for a Karmayogi.
In the first Mantra of supernatural it has been said that all living beings specially humans must have full dedication for the almighty and must remain satisfied with whatever has been given by God and never try to take anything from others because such desire is not good this is the Mantra of karmayog.

Kurvanneveha Karmani Jijivishechchhata Sama l
Aevam Tvai Nanyathetoasti Na Karmalipyate Nare ll

"In this world humans have the support of Dharma, Veda and selfless action with which he should have a wish to live on the earth for 100 years and this way according to the message of Veda and Dharma people must be practical and they must engage themselves in the action. All living beings this is what has been decided about you and there cannot be any other parts for you that might take you away from the action."
We can understand this message of Veda as follows-
Kurvanneveha Karmani Jijivishet- Aman does action in the world and he should have a desire to live in the world with this action and he must engage yourself in the action and must avoid to sit idle and waste time because this is not suitable for a man because vacant mind is home to a demon therefore he must be doing something every time.

Alasya Hi Manushyanam Sharirastho Mahan Ripuh l
Nastyudyasmo Bandhuh Kritva Yam Navasidati ll Bhartri. Niti

A man can protect himself from external Enemies but he cannot protect himself from the enemy sitting inside him therefore the meaning of the above lines is idleness is the biggest enemy sitting in us and our biggest friend is hard work there for hard working man never becomes upset in life therefore we must be doing very very hard work that will make us great.
Goswami Tulsidas Hai is beautifully written the following lines
Sakal Padarath Hai Jag Mahi Karmaahina Nar Pawat naahi.
Karm Pradhan Vishwa Rachi Rakha Jo Jaisa Karhi sojas Phaal chacha.
One can get access to the almighty only with the help of hard work that will invite in life consciousness Infuse enthusiasm and hard work and those who are always aware and have self restraint.
Ichchhanti Devah Sunvantam Na Swapnaya Sprihayanti l
Yanti Pramadmatandrah ll R. I 2 l 18
People one the earth like hard working people and hard work invite love from all sides and nobody likes the person who keeps sleeping and who is idle and waste time because the person who is away from idleness can have access to the almighty because in Upanishad it has been said that we must rise above idleness and should not waste our time because Upanishad never teach us just doing nothing and wasting time.
Here a question arises how to do action if action is necessary in life?
"Kim Karma Kimkarmeti Kavyoapatra Mohitah."
Because what is action and what is not have confused even greater Scholars and Lord Krishna has described three waves in the guitar in this regard-
Karmano Hyopi Boddhovyam Boddhovyam Cha Vikarmanah l
Akarmanashcha Boddhovyam Gahana Karmano Gatih II Geeta. 4 I 17
We must know the forms of Karma Vikram occur because the motion of Karma is the deepest motion.
There have been three departments of Karma this is in other words we can describe them as sakam Karma nishedh, Karma nishkam, Karma and mission to Karma must never be practiced and Sakam Karma keeps us shackled while with Nishkam Karma take us towards freedom and celebration therefore we must do Karma that will never let us be tied and we must do our action and our duty is to do Karma and we must act according to Dharma like we must help needy people and the people who are in pain because of good deeds and good conduct are always praiseworthy.
"Gahna Karmano Gatih" by saying this Lord Krishna has accepted the deepest secret and even after that he has said that knowledge and action both are very important in our life that cannot be rejected and moving ahead moving ahead is the greatest philosophy of life because we can never go back in our action and this is the inspiration we have got because it without you doing action we cannot live for a moment. This is Shloka in Shrimad Bhagwat-
Na Hi Kashchidkshanamapi Jatu Tishthatyakarmakrita l
Karyate Hyavashah Karma Sarvah Prakritijairgunaih II
A man cannot live even for a moment without doing action therefore according to the teachings of Veda scriptures and the messages of sages we should not be thinking about the result and we must engage ourselves in action because while doing action a man becomes free from the world and materialistic things therefore a man must be when he does action but becomes shackled when we have Expectations of result according to his wish and this way there are three types of actions one is according to Dharma another is according to our Dharma and third one is mixed one in which we make sacrifices and give directions but the money e accumulated through wrong means that is action of sinister and the money accumulated this way is donated a part of it. A man has only three means of action which our body speech and mind and does not have any other means to do action therefore protecting weaker section of society and needy people parents teacher and serving elderly people following the path of non violence not doing left gallery and never miss behaving with women are good action while in terms of speech. In terms of speech he has to speak truth and pleasant words that will be good for everyone and he should speak whatever he has learnt and he should never Goa opposite because it telling lies rough language and bad language is bad.
Our mind is the means of Sacred feel in dedication or we may also have Envy for others therefore we must follow the path shown by the almighty and Vedas because action of of a taste is bad.
There are three types of Karma - Nitya karma, Nimitta karma, Kama karma.
Nitya Karma means those who get up early in the morning at 4 o'clock and those who who do their daily evolution before the time in the night when they go to bed why Namitha Karma is the action which is done with the purpose while Kamya Karma is action that is done with the special which like footrest Yagya Drishti Yagya performed with a wish to get a child and wish for rain.
There are three types of Karma Sakam, Nishkam and Nirarthak which means the action that is done with a desire for result according to our wish while nishkam Karma is the action that is done without having a wish and nirarthak action which is useless but in Shrimad Bhagwat Geeta we have been taught to work according to this Marg and lost the calm and not sakamma Prabhavathi Marg.
Karmanye Vadhikaraste, Ma phaleshou kada chana I
Ma Karma Phala Hetur Bhurmatey Sangostva Akarmani ll Geeta. 2 l 47
Nishkam Karma means in which we leave everything ourselves and do things selflessly. This way we work with dedication and our target is to accomplish the work and the not the result is our focus. And we take success and failure equally. Such things keep us free always. This is the real Karmayoga. 
Yogasthah Kuru Karmani Sangatyatva Dhananjaya l
Siddhayasiddhayoh Samo Bhutva Samtvam Yog Uchchate ll Geeta 2ll 48
Useless action is that which are harmful for everyone and which give nothing good are beneficial to everyone because in Isha Upanishad it has been said that one will live for 100 years which is very important and and also in the four Vedas there has been a message of living 100 years as it has been said summer which means leave for 100 years while being in action and this part of this Mantra give the answer of living for 100 years.
Imam Jivebhyah Paridhim Dhami Maisham Na Gad Paro Arthamaiyam l
Shatam Jivantu Sharadah Purichirantrmrityum Dadhta Parvaten ll R. 10 l 18 l 4
I fix the limit for men that all men must live for 100 years because nobody should die before completing 100 years of life and even though someone dies before 100 years of age he should not run away from his action and we must keep in our mind that we are born not for only e Welfare of ourselves but also for the Welfare of the world therefore we must engage ourselves in great actions and never postpone our action because - 
Shwah Karyamadyam Kurvit Purvahane Chaparahvanikam l
Mrityurnahi Pratikshet Kritam Vaasya Na Va Kritam ll Geeta. 18.2
We should never postpone our action and do whatever has come to us now and whatever has to be done in the afternoon must be down that time because death never waits for anyone thinking whether you have completed your work or not.
Kal kare so aaj kar Aaj kare so ab 
Pal Mein Parlay Hoyegi bahuri Karega kab.
Therefore from this Mantra we get the lesson that our action has to be according to you always Welfare of others according to the lessons of Vedas and we must keep in mind what not to do as the action has been described in Vedas and this way we should live for 100 years and whatever we do we should be doing as the action dedicated to God.