Two different issues here.

Disappointment for not getting what you think you paid for is fine and warranted.

But ultimately it's your az riding the bike. Not the mechanic.

This is why pilots, etc. do a pre-trip inspection. The mechanic wont be going down with the ship in the case of some oversight.

You live long enough, you learn human beings aren't perfect. Nope, not even me. And you will accept it. Or not. But whether you accept or not will not change this fact. You can only stack the odds in your favor as much as possible by making informed decisions in regards to who you let touch your stuff. Or do it yourself.

It's not their stuff. It is a little unrealistic to expect them to have the same connection to it or reliance upon it as you do.  

Does anybody know where I can still get a decent haircut?