Motorcycle mistakes I've only made once:
Taking off my jacket and putting it on the seat of the bike, with part of it touching the hot exhaust.
Forgetting to put the kickstand down, or thinking it's down when it's actually partially retracted, then letting the motorcycle slowly begin its long and agonizing descent, all the while your left leg is fighting that futile battle against the unrelenting force of gravity, to prevent your expensive fairings from making heart-breaking contact with the merciless ground.
(OMFG whyohwhy did I skip Leg Days last year?!?!)
Never ever ever made those mistakes ever again.
Like... ever.
Motorcycle mistake I make almost all the time:
Leaving the key in the seat release lock and then forgetting about it and walking away from it.
Come back hours or days later. Where DF are my keys?!?!
Every. Single. GD. Time.
Motorcycle mistake I make a lot of the times:
Putting on my gloves and realizing the key is still in my pocket. @!#$@
Motorcycle mistake I rarely make, but sometimes still do:
Start the motorcycle in neutral. Get on.
While waiting for it to warm up, I get distracted or I'm talking to someone while the bike is idling in neutral.
Clutch in. Put it in first.
Ka-CHUNK. Bike Dies.
Kickstand Still Down.
Embarrassment City Ensues.
What are yours?
Taking off my jacket and putting it on the seat of the bike, with part of it touching the hot exhaust.
Forgetting to put the kickstand down, or thinking it's down when it's actually partially retracted, then letting the motorcycle slowly begin its long and agonizing descent, all the while your left leg is fighting that futile battle against the unrelenting force of gravity, to prevent your expensive fairings from making heart-breaking contact with the merciless ground.

Never ever ever made those mistakes ever again.
Like... ever.
Motorcycle mistake I make almost all the time:
Leaving the key in the seat release lock and then forgetting about it and walking away from it.
Come back hours or days later. Where DF are my keys?!?!
Every. Single. GD. Time.
Motorcycle mistake I make a lot of the times:
Putting on my gloves and realizing the key is still in my pocket. @!#$@
Motorcycle mistake I rarely make, but sometimes still do:
Start the motorcycle in neutral. Get on.
While waiting for it to warm up, I get distracted or I'm talking to someone while the bike is idling in neutral.
Clutch in. Put it in first.
Ka-CHUNK. Bike Dies.
Kickstand Still Down.
Embarrassment City Ensues.
What are yours?