I think he's jealous.

Magnus got to his feet. “I do believe that's my cue to leave as well,” he said. Clary noticed he was avoiding looking at Alec. “I'd say it's been nice meeting you all, but, in fact, it hasn't. It's been quite awkward, and frankly, the next time I see a single one of you will be far too soon.

Listen to me. I am leaving, but I am living. I will not be gone from you entirely, Will. When you fight now, I will be still by you. When you walk in the world, I will be the light at your side, the ground steady under your feet, the force that drives the sword in your hand. We are bound, beyond the oath. The Marks did not change that. The oath did not change that. It merely gave words to something that existed already.

Isabella with her whip and boots and knives would chop anyone who tried to pen her up in a tower into pieces, build a bridge out of the remains, and walk carelessly to freedom, her hair looking fabulous the entire time.

They say time heals all wounds, but that presumes the source of the grief is finite

unrequitted love amuses me

The sensation of falling was the worst part.