As Sr Developer in the company I also have a lot of responsibilities.

And after 35 years in the industry I now realize...I need down time

So:

1. Have someone cross trained to fill in on critical items.

2. Having that person ready is not a last minute thing...have it in place

3. Set my email to vacation reply

4. If anyone actually calls refer then to the mission critical person (#1)

5. Take my vacation and completely forget about work.

Doing these things allows me to unwind and return ready to work at full speed...and not as a resentfull moaner.