English Grammar - Reflexive pronouns
says the following:
We do not use reflexive pronouns after feel, meet, concentrate and relax, and we do not normally use them after wash, shave and dress, unless it is necessary to make it clear who does the action.
He finds it difficult to relax. NOT: He finds it difficult to relax himself.
When I got up, I washed. NOT: When I got up, I washed myself.
HOWEVER, when referring to meditation and hypnotism, you will read :
"We teach the person how to relax himself."
I guess they are trying to emphasize that as opposed to doing some activity to relax and take a break from work, or listening to music to relax, the person is engaged in some inner process aimed at relaxing them.
Leave that construction to the touchy-feelies, and stick with ESL's advice.