If you can play even a little bit - eg you know some hand rankings and don't get too drunk - you're better than some players, and you can find a game you can beat.
If you're the 20th best player in the world, but instead of looking to play against weaker players you yearn to challenge yourself against the best, or in general if you move to bigger and tougher games every time things are going well, you will lose money in the long run.
It's not quite that simple in practice. You might be one of the worst players in your local cardroom, so your only winning move is not to play. Or you might be one of the best, but you don't travel to other games, so you win in spite of your self. I've seen so many people like this! If you play on the Internet, however, that's effectively not possible.