I recently have switched to half time at work so I can push forward with my startup. Worked out well for me (still have some outside income), and for my company (they were dependent on me as a single point of failure, so me leaving over 6 months means I can train my replacements).

Most importantly, I've felt a renewed sense of purpose. I can't emphasize enough how much my productivity has soared and my spirits have risen.

It's scary as hell, but I've never felt more alive.