What seems to be the thing I ultimately cannot stand is betrayal. Sometimes I can let it go, and tell myself that the trespass is unintentional, but if I can no longer believe that, if I think that someone is intentionally manipulating/betraying me in some way, it's done. Every relationship is built on trust in one way or another - if I can no longer trust someone, keeping some kind of relationship with them just seems stupid.
To me, "cheating" is only "cheating", by the way, if it involves lying and sneaking about to do, if it involves betraying the other person's trust, and any kind of betrayal of my trust, I react to it as though the other person has "cheated on me", regardless of the nature of my relationship (platonic or romantic) with that person.
To me, "cheating" is only "cheating", by the way, if it involves lying and sneaking about to do, if it involves betraying the other person's trust, and any kind of betrayal of my trust, I react to it as though the other person has "cheated on me", regardless of the nature of my relationship (platonic or romantic) with that person.