Of my two experiences, the vasectomy was the most terrifying:
The work medical was just a brief look and feel of my 18 year old virgin penis by a GP. Embarrassing but ok.
The vasectomy, however, was more of a problem. I had had recurring dreams beforehand that I would be rejected from the operation because of my small size. No real justification for this but it was on my mind.
So, already stressed at the upcoming event, after dropping my trousers and getting on the table, it was obvious that my penis had shrunk to the size of a grape and my balls were almost parked inside me. At least my secondary fear of getting an erection soon subsided.
The surgeon spent ages trying to find my sperm tubes. He found one after a few minutes but took an eternity of pulling and manipulating my balls to find the second one. It wasn't helped by the female nurse saying that my 'boys were hiding'. Obviously, he needed to find both to proceed with the operation.
In the middle of this joy, he randomly commented that I had been circumcised. Still not sure why to this day but it didn't calm me down much. I just said 'yes, a long time ago'.
What must have been 10 minutes later, he finally agreed to proceed and so the cutting, burning and manipulating occurred. It took an eternity to find the second tube again for the operation. I really thought he was about to give up and leave me with one connected.
Fortunately, he succeeded. I am now sperm free and can ejaculate freely inside my wife without any worries. Worth the trauma.