Maybe you took being let go as a kind of personal rejection?
I always feel very free when I lose (or quit) a job. Then again, I always have had a support network, and more recently, savings, so maybe I'm one of the lucky ones.
The first job I quit, I think, was a crappy telemarketing scam that I felt good about leaving, and on both of the first 2 times I was let go I was about to quit anyway for school purposes, so I've had very positive associations with leaving a job.
I hope this hasn't left you without the means of supporting yourself. If you're okay, then I wish it doesn't sound trite for me to say "think of the positives".