This is a general mood-enhancing tip, not just a chronic pain tip. But hey, being in pain usually dampens our mood quite a bit, so we need all the help we can get!
Several years ago a doctor specialized in arthritis and nutrition told me that sugar in general provides extra fuel for inflammation and thus provokes auto immune diseases. I figured it would be worth a try to cut sugar completely, but never really managed to stick to it.
Last year I stumbled upon a book called "Potatoes not Prozac" while I was doing random research for my next book. It had a really interesting theory of how some peoples brains have more than average receptors for beta-endorphin, which make them sugar sensitive, prone to mood swings and more succeptible to addiction. After reading about this, and learning more from different sources, I tested a blood-sugar balancing diet for a few months, and wow, what an amazing difference it did to my mood and general productivity!
Usually, I'll have lots of energy in the morning, and always experience a severe dip in energy levels in the afternoon. My mood is generally unfathomably unstable, but when I started eating small meals every three hours and cut refined sugar from my diet it only took a few days before I was functioning at a level I've never experienced before. Big improvement is all I can say. Of course... I didn't manage to stick to it long term this time either... I think a stray cinnamon bun caught me off guard, and it went downhill from there... but maybe next time around?
This diet is apparently really good for steady and sustainable weight loss too. Which may be ok if you're not underfed and skinny. I'm quite happy being curvy, but good mood and stable energy reserve might just be worth the effort:)