For me, having a win-win relationship with someone is the key. The person gives you something, you give back. What it matters is the exchange between two people. I think whether is about respect, ideas or gifts, you share something meaningful and maintaining this relationship healthy requires you to give back. On the contrary, when someone tries to take advantage of you or trick you in any way, you will feel fooled. This can not be a basis of a good relationship. You will not feel better, but even worse. For example, a guy you dated betrayed you many times with another girl. He would always find excuses and liars. Obviously it is not a balanced relationship, you should not be committed anymore but pull out the relationship as soon as possible. There are plenty of fish at sea. You deserve better.