I just found an article by Jim Wofford called, "Are You Qualified or READY for the Next Eventing Level?". I think it makes some good points about making sure that you don't move up to soon in any riding discipline. Over-estimating your skills can have severe consequences, and I think that it's important for every rider to remember that! Are You Qualified or READY for the Next Eventing Level?
So many people jump higher jumps than they are ready for, or practice dressage movements incorrectly because either they or their horse isn't ready to do what is asked of them/what they want to do.