Doing it in the first place. Facing the blank canvas or paper, making a mark, making some more.
The sound of a brush dragging across the weave of canvas is intoxicating. I often get lost in that sound. So much so that I sometimes have to work hard to back away from the painting so I can study if it's working or not. I love the feeling of getting lost in the work. That's the best part of doing anything creative.