I know I'm not perfect and don't have it all figured out, but what I've found is that learning something new is very exciting, at first. As I begin to gather information, I immerse myself in the subject and love all the new information. Then as I find out just how much information there is, and I worry that I will never figure it out, I get overwhelmed and wonder if I should back off. If it's something that really means a lot to me (information about raising my son, for example) I keep going and find that just on the other side of overwhelming I find what works for me. Once I've found what works for me, I find that the rough patches are easier to deal with. I do still have doubts sometimes, but I've done the research and I'm comfortable with my decisions.
I don't know if this will help you at all. I'm very confident in my parenting choices and, although there's always room for improvement, I feel that I'm doing a great job being a mom to my 5yo son.