Keep close to Nature's heart... and break clear away, once in awhile, and climb a mountain or spend a week in the woods. Wash your spirit clean.
John Muir

Bitterness is like cancer. It eats upon the host. But anger is like fire. It burns it all clean.
Maya Angelou

Better keep yourself clean and bright; you are the window through which you must see the world.
George Bernard Shaw

It is well for people who think to change their minds occasionally in order to keep them clean. For those who do not think, it is best at least to rearrange their prejudices once in a while.
Luther Burbank

Clean out a corner of your mind and creativity will instantly fill it.
Dee Hock