Hollywood is fickle; your career can end pretty fast. If the acting jobs dry up, you have to have something to fall back on. In fact, that would be my advice to kids interested in acting - make sure you get an education too.
I don't know if this is why everything has worked so well and I'm not sure I'd recommend this kind of thinking to anyone else, but I've always known I'd be successful in acting. I have certainly worked for it.
I dropped the script in the fireplace, called my agent and said, they can jail me, sue me, but I'm never acting again, unless I can do something worthwhile.