It's always too early to quit.
The wise does at once what the fool does at last.
Know or listen to those who know.
By failing to prepare, you are preparing to fail.
If you think you can do it, you can.
Expect problems and eat them for breakfast.
Never complain and never explain.
Be kind whenever possible. It is always possible.
Be gentle to all and stern with yourself.
Always desire to learn something useful.
I am a teacher, and I am proud of it. At Cornell University I have taught primarily undergraduates, and indeed almost every year since 1966 have taught first-year general chemistry.