In theory, praying is all well and good. I'm not sure if I believe it has any power one way or the other, but it certainly can't do any harm.....
When I meet one of my mother's friends, and I think they're cool and we hang out for the afternoon and just as they're leaving they throw out, "and I'll pray for you" their ulterior motive becomes abundantly clear.
If you want to pray for me, fine. Don't pretend to be my friend because you think you can somehow manipulate the cosmos into making me straight.
And, obviously, in reference to the original post, that would be an example of prayer that DOES do harm. I personally wouldn't call it prayer. Don't subjugate yourself to that. Treat yourself better.