Absolutely doubts cripple us! I have lived with anxiety/low self-esteem my entire life and I can tell you from experience that doubting ourselves leads to many failures! I doubt myself so often that I get depressed and end up not leaving my house for months, seriously! I would leave to get groceries for my family but that's it. As far as my writing goes, people have told me my entire life that I have a gift for writing but I've always doubted those words. I know for a fact that I could go to school and become a professional writer, be it a writer for a newspaper or a magazine or whatever I wanted, but doubts have definitely crippled me.