Because what was the point in crying when there was no one there to comfort you? And what was worse, when you couldn't even comfort yourself?

Facilis descensus Averno
Noctes atque dies patet atri ianua Ditis
Sed revocare gradum superasque evadere ad auras
Hoc opus labor est

I should have warned her about your habit of never doing what you're told." Jace squinted at her. "Are those Isabelle's clothes? They look ridiculous on you."

"I could point out that you burned my clothes." -Jace and Clary pg. 63

We had and incident. I took care of it."
"Really." Jace's voice dripped sarcasm. "Do you even know how to use that knife, Clarissa? Without poking a hole in yourself or any innocent bystanders?

When you love someone, you don't have a choice. Love takes your choices away.
- Clary Fray

You look happy," he said to Clary. He swiveled his gaze to Jace. "And a good thing for you that she does."
Jace raised an eyebrow. "Is this the part where you tell me that if I hurt her, you'll kill me?"
"No," said Simon, "If you hurt Clary, she's quite capable of killing you herself. Possibly with a variety of weapons."
Jace looked pleased by the thought.