It's always too early to quit.
Who seeks shall find.
Know or listen to those who know.
Begin to be now what you will be hereafter.
Things do not happen. Things are made to happen.
If you're going through hell, keep going.
The most effective way to do it, is to do it.
If you can dream it, you can do it.
By failing to prepare, you are preparing to fail.
Expect problems and eat them for breakfast.
A serious and good philosophical work could be written consisting entirely of jokes.