One of my good mates back up at university started going down to the gym and a few other mates joined as a result. Thought I'd go down as well, try and get a little muscle on me as I was a skinny bugger. Carried on going since then whilst the others have all stopped.

Massive stress relief and also allows for some alone time, which I relish. I also seem to sleep more easily and am able to concentrate more. Plus, it's the only true constant of my day (discounting eating and sleeping, obviously). The visible perks of going to the gym are also great, I don't think anyone would deny that.