"He says he loves me too but when he ignored me for 5 days because he was doing an important personal project"

Just 5 days? I'd have thought - "Geez! Peace on earth"

But sorry to hear that you took it so bad that you openly flirted with some random guy. Shouldn't play games like these - less trouble for you.

"And now he's hurt. He's hurt but I got hurt first... and now he's hurting me again.."

The pair of you sound like kids fighting in a playground. But I can understand your frustrations esp if you're dealing with another insecure individual. One can only give unconditional love if one is secure himself/herself.

To the thread question -
1) we are capable of hurting the ones we love because they are vulnerable to us.
2) we would not hurt them if we truly loved them, took time to understand and have empathy for them, if we're less selfish and less egocentric.
3)But having said all that, some people are beyond redemption, at least for us, so then it's time to let go and move on.

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Beauty lies in the eyes of the beerholder.