All this is determined by Karma, work. No one can get anything unless he earns it. This is an eternal law(શાશ્વત કાયદો). We may sometimes think it is not so, but in the long run we become convinced of it. A man may struggle all his life for riches; he may cheat thousands, but he finds at last that he did not deserve to become rich, and his life becomes a trouble and a nuisance to him. We may go on accumulating things for our physical enjoyment, but only what we earn is really ours. A fool may buy all the books in the world, and they will be in his library; but he will be able to read only those that he deserves(સમર્થ ) to; and this deserving is produced by Karma. Our Karma determines what we deserve and what we can assimilate(આત્મસાતીકરણ). We are responsible for what we are; and whatever we wish ourselves to be, we have the power to make ourselves. If what we are now has been the result of our own past actions, it certainly follows that whatever we wish to be in future can be produced by our present actions; so we have to know how to act. You will say, “What is the use of learning how to work? Everyone works in some way or other in this world.” But there is such a thing as frittering away our energies. With regard to Karma-Yoga, the Gita says that it is doing work with cleverness and as a science; by knowing how to work, one can obtain the greatest results. You must remember that all work is simply to bring out the power of the mind which is already there, to wake up the soul. The power is inside every man, so is knowing; the different works are like blows to bring them out, to cause these giants to wake up.
[Ref : http://www.vivekananda.net/BooksByS…/KarmaYoga/chapter4.html]