“…But dirt riding also is usually more aggressive — the general mentality of my MX racing buddies is if you don’t crash occasionally you aren’t trying hard enough.”
:i …times 4 for trials, if you crash a section on the first lap, you still have three more times to get it right 
…positive insentive to do better.
In dirt you learn the art of front to back balance much quicker then having only ridden pavement, it’s not like you can ever learn to catwalk on a public road, how much front brake is too much, or what would it actually feel like to hop that curb in an emergency.
