It's okay to have the fear as long as you know your training and knowledge are stong enough for whatever situation you are in. During all my training I never flew solo at night and I had to finally before I could get my commercial. i was nervous even though I had many hours at night in the specific plane, in other planes also, but as soon as I was in the air it was just another flight. If you've got the training you will be able to get yourself around in an airplane just fine.

I knew a guy who was working for a 135 company who had bad maintenance, he was flying a twin, lost an engine and had an uneventful landing. Pretty much the next day he turned in his license because it scared the crap out of him... He did just fine on the one engine but i guess that experience was enough. It's all about what you want to do and think you can handle.