Flynn wants to live. He's struggling, but he wants to live. If he knew the pain it would bring to his soulmate, he would want to say he'd never have touched the knife in the first place...but he knows that might not be true. Maybe his teenage self would've felt too sick to care. 

A few people have the ability to feel the pain their soulmates do. Wounds and bruises will not show up on them physically, but they will feel it until their soulmate doesn't. This ability is called a soultie.