I have a longtime friend who used to play poker for money at high school. He had his bad streaks, but on average, due to being a better poker player than most (mostly as a result of card counting,) he was up pretty consistently, and earned somewhere around $80 per month on average, which strikes me as pretty formidable for a someone gambling with pocket money among high schoolers.
I have to admit, I don't have a tremendous amount of sympathy for people who lose out while partaking in an endeavour which is pretty much designed to have more losers than winners.
I'm not sure what the point of this comment is other than taking a dig at poker players, but poker requires a more direct application of the lessons of rationality than anything else I can think of at the moment.
http://www.washingtonpost.com/wp-dyn/content/article/2010/10/01/AR2010100105833_pf.html (one page link; original: http://www.washingtonpost.com/wp-dyn/content/article/2010/10/01/AR2010100105833.html) is a recent Washington Post article on young poker player Steven Silverman. It's interesting.
Even more interesting are his comments and other poker players' comments on Hacker News: http://news.ycombinator.com/item?id=1777385
Some selected comments:
-- jdietrich, http://news.ycombinator.com/item?id=1778364
-- matmaroon, http://news.ycombinator.com/item?id=1778597
-- tsotha, http://news.ycombinator.com/item?id=1778909
-- InfinityX0, http://news.ycombinator.com/item?id=1777624
-- bapadna, http://news.ycombinator.com/item?id=1778094 (included because it is funny)
Wikipedia on 'tilt': http://en.wikipedia.org/wiki/Tilt_%28poker%29
On Isildur1: http://en.wikipedia.org/wiki/Isildur1#Career