I don't believe in fairies

Two of my best friends contacted me yesterday, and one of them is someone I haven't spoken to for a year, and she keeps trying to reach me. It makes me feel really guilty, which covers me in shame and doesn't let me contact her, and so on and so forth in a vicious circle.
I had been asked by work to write a paper for a conference.
Yet, despite being recognised at work and not being give up on by my friends, why do I sometimes feel so worthless? Do I think so little of my friends and company as to think they are lying to me? Why can't I think that I am as good as they (seem to) think I am?

The answers to these and other question in the following episode of "Knit me a therapy". Nah, just kidding. Of course they will remain unanswered. I wish I could.