When you feel tired or find it necessary to rest, just go and rest for a while. If it is allowed, you can take a bath to repel all the mess and then you are refreshed again.
If it is not a right time to solve the tough issue, you can have a break and do anything else to relax and empty your brain, when you feel energetic, you can go back to dispose of that problem again.
At the time you sense anxious, you are probably stuck with a bad situation that you can not tackle with, you can trip to somewhere. Or you can have a quiet day in the room by reading a book without disturbance from anybody.
You can also spend some time doing exercises. Life lies in movement. Thus you can be better from workout.
There are many other ways to adjust your emotion. Whichever you choose that is enough as long as you feel good.