Every single director-actor I talked to, from Warren Beatty to Clint Eastwood to George Clooney, said the biggest mistake they made is not shooting enough footage of themselves.
Few bands in hard rock history have been so adept at balancing the awesome and trivial as Van Halen in their prime.
I think making mistakes and discovering them for yourself is of great value, but to have someone else to point out your mistakes is a shortcut of the process.