Never hold discussions with the monkey when the organ grinder is in the room.
The gem cannot be polished without friction, nor man perfected without trials.
The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man.
Whatever you do, do it to the purpose; do it thoroughly, not superficially. Go to the bottom of things. Any thing half done, or half known, is in my mind, neither done nor known at all. Nay, worse, for it often misleads.
Art is science made clear.
Speak when you are angry--and you will make the best speech you'll ever regret.
Never fear the want of business. A man who qualifies himself well for his calling, never fails of employment.