Do you know that there some people who are off limits?
If a person is messing with someone who is already in love with another, or with someone who expects a serious relationship, or with someone married, with the intention of only a new ‘conquest’ and no love, would you approve his/her action?
If your answer is ‘no‘ then you too should not do it.
If you truly love another person and realize you are off limits then stop messing with that person’s life right now. If your feelings for that person is really deep, it would indeed be hard for you and it would take a long time for you to get over your infatuation. If you do so it would be worth for your reputation, and sooner or later someone who is not off limits will come along for you to love without any inhibition, and then you will know that your decision to stay off limits was worth the wait.