My new definition for religious faith is "the suppression of doubt".I don't think that believing you will succeed at a particular task necessarily constitutes faith. And I'm not talking about that "type" of faith anyway, I'm talking about the kind of faith that leads one to believe in "something" with no evidence to support this belief, and I'm suggesting that maybe this type of thinking is not the best for our species as a whole. I'm not talking about optimism, or trust, or confidence. I think that believing in things with no evidence is bad, on the whole. I'm not talking about potential side benefits that may come with faith - I'm just talking about the act of looking up at the sky and knowing, with conviction, that god made it blue just for you. I don't think that's a good thing.
Also, I'm nitpicking, but I think that, as a child, believing in santa would not actually be an example of faith. From the child's perspective at least it is a totally rational position. They are told by trusted loved ones that santa exists and that he brings gifts - the gifts always arrive, and sometimes there is "evidence" of his passing through. I don't think the "lesson" here is that faith is good or conducive to a good childhood, but that giving and receiving gifts while enjoying a "shared illusion" of sorts is a fun thing to do.
You don't need faith to believe something. You need faith to silence doubt, so that whatever you believe can be elevated to a higher knowledge status in your mind. If we can't call that a delusion, we can't call anything a delusion.