How do your self-doubts express themselves?

This question is only for people who actually have self-doubts. No confident, on-top-of-the-world people need apply. You know who you are.

In my case, I never believe anyone really likes me. I’m constantly asking for reasons why they like me. None of the reasons ever seems convincing, though. I also don’t believe that anything I do is really helpful, or if helpful, helpful enough. I think that everyone else is doing better than I am, in terms of friends, income, skill, talent, effectiveness, etc.

You? Can you tell us about an incident in your life that illustrates how your self-doubts play out? Do you have a theory about where the self-doubt comes from? What have you done to attempt to deal with self-doubt?