Men of ill judgment oft ignore the good that lies within their hands, till they have lost it.

How dreadful it is when the right judge judges wrong

Don't judge me as if you are a saint. Don't look at me as if you haven't sinned.

Consult your friend on all things, especially on those which respect yourself. His counsel may then be useful when your own self-love might impair your judgement.

You may know a man by the company he keeps

Good judgment comes from experience. Experience comes from bad judgment.