It depends, nothing is ever that black or white. Sexual repression is a difficult subject to talk about, since there are some urges one should never even think about doing (pedophilia, bestiality, rape), due to the damage it can cause to third party participants.
Now when talking about a coworker or teacher, I honestly think it's okay to at least try. A lot of people develop feeling for teachers, due to puberty and the raging hormones, but most of the time something like that fades away after some time.
Coworkers is more difficult. Inappropriate sexual actions can cause a lot of damage, which can even go as far as to get you fired. But as I have stated before, one can always try, but know when to stop.
I have mentioned pedophilia, bestiality and rape, and those urges should NEVER get acted upon. It's disgusting and against the law, for a reason. If one ever feels such urges, they should immediately talk to a psychologist.
That's my take, act upon if no one is getting harmed, or at least try, but somethings should never be done.