Just a couple of days back I was discussing success with a friend of mine. During the course of our conversation I uttered this line, "If you are happy with what you have then you are successful." The line has stayed with me ever since.
As the old Hindu saying goes, "Aadmi apne dukho se itna dukhi nahin hai jitna doosron ke sukho se" -(TRANS: A man is more sad about the happiness of others than his own worries). Success is a combination of luck and efforts. Some people have both and become the objects of envy for most. For others it's a combination of the two or none.
We should realise the fact that every individual is different, and that is our biggest strength. Let luck not affect your efforts. You may or may not succeed but at least you will always take pride in the fact that you gave your best shot to realise something. The secret is not to compare yourself with others but with what you 'were' and where you 'are' now.