Dear Amelia:

It may be a good idea for you to leave this job, but before you do try to accept what you cannot change, this  acceptance, if  you manage it, will reduce t he resistance, the  friction that you experience  daily at the job, and that friction I s what is tiring you so much, the resisting of it.

See  if accepting  the way things  are while  maintaining some rules (to not  be abused, for  one) makes the work situation  less unpleasant and  focus on what is pleasant  about it.

anita