Chances are you are doubting yourself, your ability to achieve things, to advance to the new level.
You know what's even worse than doubt? Regrets.
Regrets of the things we didn't do when we had a chance. Regrets of the time we didn't spend wisely. Regrets of the challenges we didn't take.
Don't wait. Jump in and swim.
PS If you prefer to get wet in small bites, you can of course wade instead.