"Don't,"
When the word left his lips, even in the middle of an alien attack and the man he loved dying in his arms, he couldn't stop the truth. No one should ever love him. Not for their sake, though in the end, those that loved him always turned against him or suffered for their love. No, his reason for not wanting to be loved was all about him. It hurt too much and he simply couldn't bear it any more.
"How many children do you have?"
When Gwen questioned him, even as the scratch of twin dug into his wrists and car lights, which shinned light a sick beacon shinning the path for his fate to follow, twinkled on the curvy country road he didn't want to reveal too much. After all, what did it matter? So many lives he had lived but only half lived. Lovers abandoned before they could age without him. Children left behind before they question his never changing appearance. Lovers and friends dropping all around him like petals drying up and falling off a dying flower. And the worst, people he had held close to his heart that turned on him out of fear, or greed, or hate. He lived only half lives, stories without endings or endings without joy. That was his fate.
"I'm sorry for your losses"
He had been honest with John. Well, honesty as defined by a pair of boys who were running from their past lives, desperate to create new stories for themselves. John was such a danger when he was around. But the danger was not in the physical, not really. It was in the truth that lay just an inch under such thin skin. John was closer to the real Jack than anyone at torchwood, even Ianto, would ever know. And even within the monsters that both he and John could be, there were moments of such warmth his whole being ached, even now, at the loss. To boys clinging together, trapped in a time loop. Lost in each other. Whispered promises, delicate touches, less than delicate touches, laughter and love. He had every intention of going back to John until he met the Doctor. The Doctor always changes everything.
"Just looking at you, you're wrong"
Time travel can mess with your perception but, it plays even greater havoc with your relationships. When Jack first met the Doctor, thought he found him exciting and fun, he didn't really fancy him. Not strongly fancy him. But, when he met his regeneration, well, damn. But, you don't get a bigger bucket of cold water than the man you are hot for telling you that your very existence is wrong and hurts his head. A migraine, a mosquito bite, the stink of a Weevil all of this would bother the doctor less than being in the same room with Jack. Of course, by the time they reached the year that never was Jack had already glimpsed the future and knew his friendship with the Doctor had been more than repaired. Just a short trip into the future, the knowledge of just how sexy a bowtie, casually tied around a bedpost, could be, pushed him through the year that never was even when he was unsure he wanted to survive.