I had several experiences to question my decision to take up flying helicopters in the US Army...far too many actually.
The one that stands out most was when I had a .51 Caliber Round remove the left pedal from under my foot, start a hydraulic fluid fed fire under my feet while carrying an underslung load in cloud.
The North Vietnamese Army gunner and I both had a very lucky day.
He hit my aircraft and missed me.
We were quite busy for a while....but ultimately made a safe landing at a Special Forces Camp from which I was medevac'd with burns and a shrapnel wound.
Yes....it stays with you....and it is after all the fun and games when you have time to contemplate everything that happened that the deep down cold realization of how close you came to snuffing it gets to you.
There were other times when you knew ahead of time the LZ was "hot" and you were without doubt were going to get shot at that gave time for the worry to get up close and cozy too.
Being scared is easy....saddling up and carrying on without showing fear to your subordinates is the hard part.
I learned it is wise to never fly with someone braver than you are.