That nagging self doubt

I am the queen of self doubt.  I really am.  I know it drives T absolutely crazy, but I constantly doubt myself.  Or critique myself.  It's ingrained in me, and I can't help it.  I am my worse critic.

It's the constant voice in my head saying "you can't do it...you're not going to be good enough."  It's like the "it's a small world" song in my head.  I can't turn it off.  It's always there.  With my job, I may appear as confident as can be, but I'm thinking "what if I don't win this trial?  What if I mess up?"  When I took the bar exam, I had myself convinced for months that I had failed it before I saw the evidence that I passed. 

Sadly, the self doubt is following me into my new ventures.  With my new job, I put on the hat of "boss."  I have to make the tough decisions, and the buck stops with me.  And I would be lying if I don't hear my inner voice constantly saying "do you know what you're doing?  What if you can't crack it as boss?"

And the Mary Kay, I'm constantly thinking "well, what if people don't buy from me?  What if I just lose a bunch of money?"  I'm only 3 months into this venture, and I have myself convinced I'm going to fail.

The same goes with writing.  I sat down yesterday and got back to my manuscript, but in the back of my mind I'm asking "what if this is crap?  What if no one reads this?" 

And it's not the big things either - just ask T.  I'll make a meal and as we sit there eating, I go, "is it good?  Are you sure you like it, or are you really just saying that to make me happy?"

Some people call that being a pessimist.  Some people call it being hard on myself.  I call it being Nain. 

But no seriously....how do you shut that voice out?  Back in college, after a rather rough break-up, my cousin, Emily, tried to keep me strong and positive by making a series of signs she made with paper and bright marker listing each reason why I didn't need to get back together with the jerk who dumped me.  (I did end up getting back with him and then broke up again, but...not the point here...)  They were there as constant reminders to strengthen me and keep me centered.   Because I would have those moments of weakness where I'd want to go back to my old habits and give him a call, but I'd look at those signs and go "oh yeah, that's why I don't want to." (Editorial note:  Those signs were no longer there in my new dorm room when I did get back with the jerk.  That could be why I faltered.)

So maybe I need signs around my house.  "You can do it, Nain!"  "You're a good writer, Nain!"  "Your meals don't taste like ass at all, Nain!" 

Or maybe I need to go all Stuart Smally on this and sit in front of a mirror going "I'm good enough, I'm smart enough, and gosh darn it, people like me!"

Regardless, something has to give...any suggestions?  Am I the only one here who has this issue?