Love is the strongest power there is.
Fame is a fickle friend, Harry. Celebrity is as celebrity does. Remember that.
You have to kill a lot of trees before you write anything good.
Neville will play Quidditch for England before Hagrid lets Dumbledore down.
They don’t need walls and water to keep the prisoners in, not when they’re trapped inside their own heads, incapable of a single cheerful thought. Most go mad within weeks - Lupin
The knowledge that you have emerged wiser and stronger from setbacks means that you are, ever after, secure in your ability to survive.