I paid the yard by the hour for the mechanic's time, not a set fee to clean the tanks. Am I disappointed that there's still dirt in there? You bet. But there are parts of that 800 gallon tank that aren't accessible. I should probably be annoyed at the Ossining mechanic who only tightened the nuts on the tank's access cover hand tight, but he probably didn't figure on me almost sinking the boat and getting water in there.
I dunno, I guess I just find it easier to get through life not letting the little things get to me. I'm much happier that way. I realize that people are human, and like me, make mistakes.
BTW, in my computer business, I told every new hire that he or she would never be fired for making a mistake. The people who make mistakes are the people who do all the work. I would fire someone, though, for making a mistake and then covering it up. This formula worked well for me for over 20 years.