I noticed when I changed my diet to Primal that my mood improved and I lost that sense of doom that eventually I was going to have an emotional blow-out and get fired was lifted. That was probably the one change for me that actually made me more excited about Primal than losing the weight.
This summer I met a friend to go backpacking. He told me that he had recently changed his diet to one that he got from Food Addicts in Recovery Anonymous. Basically they do not eat any flour (no flour from any kind of grain, but whole grains cooked whole are okay) and no sugar. They are instructed to consume at least 1/4 cup olive oil at every meal. He told me he was shocked at the personality change he had.
Before he went on this diet, his wife had gone on the diet and had lost 130lbs and had ceased to engage in the bickering and snapping they used to do to one another. She was able to cut her anti-depressants down to the absolute minimum dose. She'd give them up altogether but she's afraid to with her super stressful job.
He told me of how he was hiking in New Mexico and met a man who owned a bakery who said he did the same thing, went on the paleo diet or something like it, and his health improved, weight improved but best of all, he no longer needed anti-depressants or whatever he was on.
All through this hike he and I discussed how much this simple diet change had improved our lives. It was really amazing to us. I had taken anti-depressants back in the day. I stopped taking them a few years before I went Primal, but I still ended up with permanent ringing in the ears. I know now that I never needed them to begin with. Oh well.
Female, 5'3", 50, Max squat: 202.5lbs. Max deadlift: 225 x 3.