You note that exercise releases endorphins and boosts mood. I've never experienced that (or anything like a runner's high), even when I was younger, but I'd like to. Exercise has always felt painful to me, and as an adult, I've become exercise intolerant due to fibromyalgia, widespread tendonitis, and osteoarthritis in my knees, shoulders, neck, feet. If I workout to try and improve pain in one area through strengthening, it always results in a serious problem developing elsewhere in about 1-2 weeks, and then I have to stop doing everything and wait months for the pain to calm down. This happens even if I begin slowly - for example, I tried an armbike at no resistance for only 15 seconds, at it caused a flare up of bilateral shoulder pain so bad it took several weeks before I could sleep on my shoulders (and therefore sleep through the night). I really wish there was a way around this. I've tried yoga, cycling, water exercise, etc. to no avail.