Epictetus:
The chief task in life is simply this: to identify and separate matters so I can say clearly to myself which are externals not under my control, and which have to do with the choices I actually control.
Richard Osman:
Learn to count the good days. Tuck them in your pocket and carry them around with you.
Eihei Dogen:
If this one day in the lifetime of a hundred years is lost, will you ever get your hands on it again?