I don't bet constantly, just on/off at an event or sport I feel comfortable with but nothing has been successful. I have had a couple times where I won big but the losses far and away outweigh the wins.
That's the main point. If you don't follow the sport consistently you'll have a hard time making money. I know some people who just pop up once in a while here and don't bet during their off times. This is not enough imo.