Relying solely on a helmet seems like a really bad idea. I recommend learning how to fall using your hands/forearms and not damage them at the same time.

Martial arts training (judo would be a good one) can help a lot here.

There are also a lot of context specific tricks you can pick up. Like if you fall skiing or snowboarding make a fist when you put your hand down instead of falling with an open hand. A fist vs. open hand won't make much of a different on snow, and the fist will stop fingers/thumbs from catching and breaking. In addition the wrist is less likely to break.