I completely understand how you feel. The few days that I've felt good in the past few weeks have been great, but I've been so down the other days that it's hard to do anything. I just want to take a baseball bat and smash everything around me. And my wife is getting tired of me joking about jumping out the window.
It's funny how dreary the world (and future) looks when there is no end in sight to the pain, but on the good days everything is rainbows. What I'm dealing with right now is probably just a minor setback, but it still hard to take. Those of us who've been dealing with this a long time just have a hard time tolerating much more. I guess we just need to lower our expectations, quit expecting to get better soon, and just enjoy it when it eventually happens. As my wife says, "it is what it is."