'You only hurt the ones you love,' The Doctor shook his head at the phrase. You didn't just hurt the ones you love, ultimately you destroyed them. No matter how much you tried to prevent them from coming to any harm.
He'd spent years with his love, only for time to finally catch up and take her away from him, he tried to fight but each battle only served to strengthen time's hold and weaken his own. But he wasn't the only one fighting, he was part of a team and if he was completely honest, well. She'd always been his kryptonite.