Some opportunities are expensive because they consume attention rather than money.

Some opportunities cost very little money and take over your mind. The project you keep thinking about in the shower, the obligation that sits in the back of your head, the thing you are half responsible for. Attention is the scarcer currency and the one least tracked, and it can be fully spent while your calendar still looks open.

List the things currently occupying your mind rather than your diary. Close or hand off one of them. The relief is usually larger than removing several appointments.