Try to look past the morbidity and enjoy.
The Man of Scars strolled nonchalantly down the busy streets. He loves these streets, for they are his only comfort nowadays. Now he walks with a cane - caused by a terrible accident with a demon years ago- but he doesn't mind, quite the contrary, he enjoys it, it makes him feel powerful, and he loves the sensation of power. He chuckled slightly to himself, Clary definitely would have reprimanded him for such a Valentine-like thought. Of course it didn't matter now, she wouldn't ever reprimand him again, she would never speak again, never breath again. On days like this he felt a twinge of guilt when thinking about the day he had killed his wife and her lover. He remembered closing his strong, scarred hands over her porcelain throat and squeezing until her life left her body. The way the bright light left her piercing green eyes, the way he laid next to her unable to cry, unable to look away. To love is to destroy, and he loved her most of all. Of course, he had killed him as an afterthought, her lover found what he had done and began to scream. A good, quick knife to the heart stopped his panic. He winced slightly as he put too much pressure on his partially healed leg, it seemed to be the only thing tethering him to reality. It didn't matter, Jace reckoned, the world was much better off without Clary and Simon.
(A/N) Originally, I was going to have a different twist and instead of Jace, Clary and Simon, I was going to make it about Simon, Isabelle and Meliorn, but I decided that was too stupid. Still a bit morbid.