He had a bad habit of disappearing.

He preferred the term 'disappearing' over 'running away,' though there wasn't much difference in the two. The moment he became to attached to someone he was gone. This was a problem that had arisen only recently; he'd never made such relationships until half a year ago. It terrified him to think what may happen to them when he figured out who he was. To put someone he cared about so much on the back-burners; well the thought tore him to pieces. People like Tex and Drowsy or Malachite and Chance—would he ever see them again when he found his way home? He'd planned for three years to never leave again when he'd made it back to whoever was waiting for him. What if he wasn't the same person he was now? What if he was the kind of person to let those friends he'd made just fade away? The possibilities made him want to scream.
And then there was Joanna. She terrified him the most. Had he meant that? What he'd said? Did he really love her? Well he certainly enjoyed her company. The time he'd spent lounging around talking to her was some of the only moments he could felt like he could "forget the fact that he forgets." Not to mention how happy he'd felt the night before just waking up next to her, even if falling asleep had been an accident in the first place.
Over the past few years he'd had a fling or two—nothing he didn't feel guilty about, but nothing that truly meant anything to him. Physical and emotional relationships were two completely different things in his head. He could justify a very, very short-lived physical relationship but an emotional one—that was what he had to avoid. After all, what if he had someone waiting for him? A girlfriend or a fiancee or a wife? And then the thought that would make him overflow with guilt—what if he had a kid? He was only eighteen when he'd lost his memories so he'd tell himself it was a ridiculous thought. In some villages and kingdoms though it wasn't unheard of to start families as young as fifteen.   
And so here he was, running. Maybe it would be better if he just left them all behind now. Let them hate him so they didn't notice when he stopped coming back. He'd spent two and a half years alone, he could manage that again couldn't he? Just because he'd got accustomed to company over the past six months didn't mean anything. The fact that he'd been remembering things better since then was just a coincidence. Before he'd started building relationships with people he'd searched more kingdoms and villages anyway.
Never visit the same place twice, he thought. Remember that?