Boredom

"Is life not a thousand times too short for us to bore ourselves?"
-Friedrich Wilhelm Nietzsche

"Are you bored with life? Then throw yourself into some work you believe in with all your heart, live for it, die for it, and you will find happiness that you had thought could never be yours."
-Dale Carnegie

"Everyone is a bore to someone. That is unimportant. The thing to avoid is being a bore to oneself."
-Gerald Brenan