RE: What
The dumbest (and most fun) thing I have done in relation to R/C is get involved in the hobby. In the past 25 years I've had (and still have most) over 150 cars, a dozen planes, half dozen helis, half dozen motorcycles, and a dozen large scale gas boats. I could have bought another house with what I've spent! With my obsessive compulsive personality, things can spiral out of control rather quickly when a hobby turns into a passion.
But you only live once, so you better enjoy it! So.... No Regrets!