What Krishna taught was to do your duty and live your life without attachment to fruitive results. I'm afraid that material goals and achievements fall into that catagory. Again, this is not wrong or bad but it will keep you in the material world. If you are a good person and work very hard then you ar elikely to be born into a good life; but that life will still be in the material world.
I should emphasise again that to attain liberation the equation is not:
losing desires ---> moksha
it is:
Discover God---> lose desires
As we become closer to God we lose attachment to fruitive work and things material. It is a natural process. In the meantime it is important to strive to be a good person and to do good. Being lazy is not good because it is a sign of being in the mode of ignorance. Having determination and motivation to doing one's duty or to reach your best potential is in the mode of goodness. It is a good thing but the need for it, or desire for it will slowly disappear as you come closer to Realisation.
The human body is wonderful as it allows us to use our intelligence and morality and empathy to further ourselves in both spiritual and/or material ways. But remember that we have been through every form of life including germs and plants etc. We have existed forever. We are incredibly fortunate to finally be in a human form. But even in this human form we are trapped by maya, which is the covering of this universe. Maya creates the illusion of duality. We think we are completely seperate and we are generally selfish creatures. We cannot understand our connection to the Divine and to everythign in existence. So we do care about being better than others in our class and so on. When we finally realise that nothing we do in this material world that is not done in God Consciousness is a waste of time then we also attain liberation.
Nobody here is at such a stage, or even close. If we were, we would not be in this world.
If I had the choice between attaining Moksha or to better the lives of those less fortunate than myself, I would choose the latter. An Atheist who is spending his life helping others is not doing it for some "higher" purpose, he is not even thinking about getting to Moksha, he is doing it so that others can be happy. That to me, is finding God.
Make a difference in the lives of others, and you will surely find God.
As for desires, I have already posted why desires are necessary and beneficial. Please see my example about the desire for a shirt in one of my previous posts addressed to you.
Another point about desires, first we are born out of desire, don't you think? A desire between man and woman.
Second, we go thru life desiring a lot of things - a desire to get good marks was my thing in school. I assume you are an adult - give me an honest answer - would you advice your own children or relatives children not to aspire for higher marks?
As we grow to adulthood, we have other desires - a desire for a good job, to make our parents happy, to get married, have children, a desire to see the children make good, a desire to see them be safe. If you were the mother of son who was in the army and a war broke out, don't you have the desire to him be safe and sound?
And then finally we reach old age. All our responsibilities are done, we lose the ability to do a lot of things, to enjoy many things.
Ah, now we get to finding God - let's lose desires! How convenient.