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.