Nuggets of Wisdom - What are the most valuable ones you got? Did you imbibe them?

Pretty much the title.
What are the wisest things you've been told by people you've known (hence, excluding typical quotes, books etc.)?
Was it easy to practice them in your life? Was it easy to? Do you still try, or were they forgotten?

For me, it was:

• A wise person knowns what to ignore.
• Don't fret the small stuff (was recommended the book)
• See the big picture.

I remind myself these, but often forget. In some phases, they have been invaluable, and have saved friendships.