I understand what you mean. I also sometimes think things are getting better, or will get better soon, then I somehow am back to *hopeless*.
And I know, I can wake up one morning in a great mood, then I'll get a call from my mom complaining to me, then the rest of my day is sad and despondent.
So, know that you aren't alone in what you are going through... I think somehow there must be a way out of this.