I went to a tradeshow for my company a few weeks ago, where I got to just interact with potential customers all day. I had an absolute blast, by the end of the day where the other folks on the team were tired and ready to leave (I was the only developer), I was pumped and already thinking of how to come across even better to clients at the next day of the show. It made me realize how programming has adversely affected my demeanor and way I interact with people.
I realized that not so long ago, I was actually outgoing and cheerful most of the time, but programming has made me more surly and sometimes reactive in an insidious way. With programming you're always dealing with problems, and if you're not solving them in code, or being infuriated by something that you thought would take 30 mins but has blown your entire day, you're dealing with people problems.
"Why isn't this done?", "Why should we pay that much?", "When is it going to be done?", "How long do you think its going to take?", "Why is it going to take that long?", "Can you just squeeze this one thing into the iteration?", "That sounds easy", "Why is this broken?", "Who broke it", "Why can't you just code", "You ask too many questions" ... aaaaaack.
its just this steady barrage of crap you have to deal and you're usually the one saying "no", "we can't do that", "Why do you want to do that?" to where you just become this proxy for negativity even if you don't want to be, because ultimately you're going to be the guy cleaning up the shit when everything explodes because nobody thought to figure out how to do the whole thing properly.
Unless you're working at a real top notch engineering place, where half these questions don't come up or the top brass understand how the whole thing works, it can really mess with your attitude.
When I had that epiphany after the tradeshow, it really freaked me out to realize how professional programming was changing my attitude to people and life, so I don't think I'll be doing 100% development for much longer.