I sometimes wonder why I keep doing it. I wish I had a better answer for myself than, "I'm just into that." Unfortunately, it isn't life-threatening. I say "unfortunately" because, were it, I would either be too scared to develop the habit I have, or it would be a negative feedback-loop and, thereby, lead to its own end.
Sadly, it isn't. I keep doing it, and I'll continue to keep doing it probably as long as it'll work. Who knows? Maybe it'll stop hurting one day and I'll lose interest. Or maybe the exchange (or lack thereof) will change and become positive. I doubt that, but apparently I'm into disappointment.