The only person who never made a mistake is the person who never did anything

Engineers don't enjoy making mistakes.  It hurts,  it's painful, it can be expensive, it can be humiliating, it can be dangerous.  Failure can be all of those things and more.  Which is why we need to be mentally tough.  We lead and sometimes we take one for the team, but ultimately we are Do'ers.  So learn from the mistakes, manage them and move on.  
And when the going gets tough, remember,

 "The only person who never made a mistake is the person who never did anything"

We don't have problems – We have Opportunities for Improvement

Sometimes there are VERY BIG opportunities
 

Yes,   this is a difficult problem – But if it was easy, anyone could fix it and you wouldn't need me

There are times when the problem is difficult and there isn't a quick, easy fix and when people are on your back, there can be a need to remind them of the realities of life - nicely

A Short Pencil is better than a Long Memory

Write it down, record it - In a note pad,  back of the hand,  PDA,  whatever is handy.
It doesn't need a long story, just enough to ensure that you have captured the issue and that it will jog your memory