Depression and Happiness -
Depression: when you're waiting not to do things;
Happiness: when you can't wait to do things.
I thought of this saying when I realised that when I was depressed, I stopped myself from doing things - I put obstacles in my way.
When you're melancholy, it's like when you're in your garage and the engine won't start. When you're contented, you're revving the engine raring to go.