I've been thinking of this lately.
I sometimes see first-time customers (first time for me), who are extra nervous about the mastering, and when the thing is done, they're really relieved to hear the outcome still sounds what they mixed it to sound like, just much better.
This is of course how it should be, but it feels kind of stupid to assure these folks that I'm not going to butcher their sound because I'm not deaf.
In the past, they might have had a bad mastering experience with another project & engineer, or maybe they just have a general feeling that mastering is the stage when a lot of random factors are bolted on and things might sound like crap, great or anything in between. Even sadder, sometimes I'm told about records that sound like crap after the mastering, but in the hurry (or for whatever reason) they moved on and regretted it later.
Whatever the story is, I sometimes feel bad to sit in a position in where I'm suspected to go berserk at any random time, just because I'm mastering engineer.
It's like a "all cops are violent bastards" type of a thing.