Once you start reading the hate, you don't stop. You repeat the words over and over in your head until you believe it's true yourself. It's not going to stop, you'll just have to learn to live with it.
Always being a little more sensitive when it comes to critic, Ashton finds himself having a hard time dealing with the hate, that comes with being famous. His band mates, however don't seem to notice, they themselves don't have a problem when it comes to hate, they simply learned to ignore it. Ashton didn't. He never learned how to do that. He had already cut before and managed to stop, for the band, for the fans, for his friends. But the constant hate seems to trigger it again and this time his friends don't realize what's going on, except for Luke. He notices soon enough, at least everyone hopes that it was on time.
The last thing Ashton ever wanted to do was hurt Luke, but he couldn't help it. The singer was just so beautiful, so ethereal and otherworldly that it took his breath away most of the time. Everyone felt that way about their best friend though, right? It was normal. No use getting unnecessary feelings involved, it was better this way. Luke understood.
Luke wasn't sure when this thing between him and Ashton started, or how it started, but it didn't matter. He was in too deep to go back now. So Luke would let Ashton use him, hurt his feelings and crawl back with apologies. Because at the end of the day, even when Luke had to watch Ashton leave the bar with a new pretty blonde each night, he knew the drummer would eventually end up back in his bed. And Luke told himself he was okay with that.