Never

1. Give the same presentation twice. Pitch or work-shop. Key-note or lecture. There is always something you can try and improve. It's good for them and it's good for you.
2. Micro-schedule your day. You'll have to rely on reptile brain to survive. And you know what happens then.
3. Do 'very special' deals just in order to close the quarter or close the year. The subsequent quarter or start of new year will be particularly painful. No-address the deeper problem. ASAP.
4. Assume a relationship can't be fixed. If you want it to be, try to.
5. Blame the economy. A good entrepreneur uses plan B; you do have one of those, don't you?
6. Say never.