Stress can be a cause.
It is obvious, but you have to relive the stress in other ways.
No magic cure, but exercise, a healty diet, a good night's sleep all play a part long term.
In the immediat eterm, make sure you "switch off at night".
Stop working, and give yourself two yours to yourself.
Watch a film see friends, read a book etc.
And it may not be possible but could you assign 20 minutes in the morning to reading a nice book before work?
But I understand if that is hard, the morning is often rushed.