I recently read an article that talked about the beneficial effects of endorphins on the brain and body, even for those with an autoimmune disease or cancer.
Here is a passage from the article :
"Some people believe that these endorphins reduce symptoms of auto-immune diseases such as MS and even modify other chronic diseases. Endorphins also seem to promote healing and repair of tissues as well as have a positive effect on immune cells; opioid receptors are found on immune cells and some cancer cells. Stimulating the opioid receptors may cause programmed cell death (apoptosis) of cancer cells."
I go to the gym, get a pump, produce some endorphins, and can feel good about the effects the workout has on more than just my muscles!
Whether your thing is working out, running, cycling, swimming, Zumba, or whatever, get into it for the endorphins - and their beneficial health effects!