Confidence in your bike and yourself, and a helmet.
The only thing holding you back is the fear of failing, and if that's all you think about when lining up for the move, you pretty much definitely will fail.
Tell yourself you can do it, and you probably will succeed.
If it's a gap that you know you can clear because you've done the same distance but on smaller things in the past, then you're just cautious of the fall I guess.
If you're eyeing something up and taking a punt at doing it but have no idea wether you can actually make it, then we can't help