Education is a progressive discovery of our own ignorance. Be miserable. Or motivate yourself. Whatever has to be done, it's always your choice - David M. Burns/ Wayne Dyer/Will Durant - various people have claimed this one!
There are many such quotes expressing this idea. One of my favourites, of course, is from Groucho Marx: I, not events, have the power to make me happy or unhappy today. I can choose which it shall be. Yesterday is dead, tomorrow hasn't arrived yet. I have just one day, today, and I'm going to be happy in it.
Here's another: Your attitude, not your aptitude, will determine your altitude - Zig Ziglar
Anotherof my favourite quotes from Qui-Gon Jinn is even more succinct - your focus determines your reality.