Is it possible to change our destiny through prayers and/or puja?
Well, puja certainly changes a person so that you are not as harmed or vulnerable to the vicissitudes of life. If rain itself is inevitable, prayers will not aim to change the weather, but rather, equip you with the umbrella and raincoat that you need to face it.
There is no doubt about the boundless power of God's name. It has the strength to even change the course of one's fate. However, destiny is made by actions themselves. With each and every thought you have and karma you perform you are sowing the seeds of your destiny. The results you reap are what you call your "fate". If good karma and thoughts are your seeds then you will inevitably enjoy a wonderful crop. However, even if your seeds were bad and a situation comes your way, which cannot change, its power to hurt you can be less depending on the actions you choose today. Good thoughts and karma will always protect you both ways, one, by being your shield today and second, by flourishing in the future. And then, even when good things happen and come your way, action is still needed! This is a constant cycle where there will be ups and downs but the strength of a devotee comes from his unwavering faith. No matter how hot it gets outside, a Bhakta constantly enjoys his internal air conditioning. He thinks "I am God’s, God is mine and wants the best for me. Whatever God does, is for my good. This belief will never leave me."
Some of the above is from an original document, which unfortunately, I do not recall where from!
