To a very large extent, poker is a game of logic. The professional players you see winning time and time again do so because they are able to keep things in perspective, even when the game gets fierce, even when the hand they are playing is particularly the nuts.
People are by and large drawn to poker because it is one of only several betting based games wherein winning is actually a possibility. With casino betting, whether you are at a bricks casino or playing online, the odds are generally stacked against you, no matter what you may think. Roulette, craps — there are no guarantees, even in Blackjack, unless you know how to count cards.
A lot of people never play poker because of the money — they play for fun, enjoyment, and entertainment. However, just as many players are in it for the money — and that is where things can get dangerous. You may not necessarily develop a gambling problem, but you don’t have to be addicted to lose a butt load of money.
Never, ever start playing because you think you can get rich quick. By the same token, take every loss with a grain of salt. When you start thing you have to win your losses back immediately, you’re in trouble.