Sometimes the fear won't go away.
So you'll have to do it anyway.
There's a very fine line between the edge of not doing something because doing "it" is dangerous or not advisable and it's just plain so out of your realm of experience that it's scary.
Same thing goes with pain, pain management, and rehabilitation.
Where's the edge between pushing yourself beyond the comfort zone and it's okay and pushing yourself past the edge and suffering a set back in your recovery? Honestly, trial and error is the answer. You learn to listen to your body and know when to push and when to pull back.
Back to moving ahead into the unknown. The unknown bubbles up fear because it is exactly that: the Unknown. What if you go ahead and DO IT and now it's no longer unknown? Now it's an experience. And you know what? It wasn't so bad. You may wish you'd not done it, but next time you'll choose no from a place of experience and not fear.
I teach my clients that to get to something new, you have to...