I am not smart enough to have thought to say these But I think these are good quotes from a great man.
"Do your duty in all things, you cannot do more, you should never wish to do less."
"Say just what you mean to do on every occasion and take it for granted that you mean to do right."
Robert E. Lee
and here's the homespun version of the latter.
"Make sure you're right and then go ahead"
Davey Crockett