I have seen many, many first backflip attempts over the years. Personally, I ate shit on my first attempt on a park jump.
From my experience the biggest fails are:
Smacking your head off the lip.
Issue: Person gets over excited, worried about under rotation and hucks too aggressively.
Fix: Take the dudes advice above.
Stalling the rotation / catching your tips on the knuckle
Issue: Person has poor body control and air awareness, or simply hucks it and hopes for the best.
Fix: Go BIG on the tramp and diving. You want to be able to do nice lazyboy backflips in training so you learn Try a backflip off of a 2.5M or even 5 M platform. Having a lot of air time is key because it will teach you about body control, timing, making adjustments in the air, air awareness, and confidence.
If fear is your biggest problem, my best advice would be to just accept that you are trying something dangerous, and you are risking injury. But you are totally OK with that because you love skiing, you want to push yourself, and every single decent freeskier had to go through the same moment at one point or another. good luck!