This industry is cruel. It’ll make you feel stupid on a daily basis. It'll remind you of how dumb you once were or how your old decisions have lead to the terrible situation you're in now. You've got to really love this career to put up with this.
The second thing I'll say on this is feeling stupid is a good thing. It means you're learning. Stick with it. It may be cruel, but it's just so rewarding. Stick with it.
Heads up: As with any terse bit of advice, there will be exceptions of course, and subtleties and nuance that can't possibly be captured in a Byte of Wisdom. This has been what I've experienced, I'd love to hear yours in the comments too!
You can catch up with all the other bytes at http://bytesofwisdom.com/