Everyone has a certain amount of happiness and a certain amount of distress and it's dependent on your karma. By our work, we cannot change the happiness we get. We work so hard, you can work as much as you like, still not happy.
But karma can change by pious activity, so in that way, you can do something about your destiny and you can improve it. But there's different types of piety. Material piety will give you material benefit, but piety related to Krsna, that is another thing.
That is the kind of piety that can change your life!
(Kadamba Kanana Swami, Durban, 04/04/2010)