'Clara, I'm not your boyfriend.'
She watched him like she could not believe that he had revealed her ultimate secret, one she wished that she could deny, but it was all too clear that neither of them could avoid the subject which had already made an impact on their short relationship since the change.
Watching her disbelief glance over the new man made him consider how much their position had changed in relation to one another. He thought back to his past life and how they would be standing closer together had they been having this conversation. The way he had flirted with her in his past body, he had to accept that his behaviour with his young earth companions in recent times had been done to sate an unstoppable appetite that most sentient beings have for closeness. The previous body, indeed the past few regenerations, had made it easy for him to forget his true age and take advantage of what some humans might describe as his 'good looks'.
The bodies had been bold, young and flirtatious. In previous times, he had been resolute and stuck to a strict self-discipline not to associate too closely with those he travelled with, but as he speedily rushed through regenerations in quick succession, he realised he had become careless with his own rules. He knew the restrictions he put in place were the right thing to do for someone in his position, a man who travelled in time with everything at his disposal if he wanted it to be, but as each life continued and realised that the looming shadow of death was real, those men had decided that to make life worthwhile, to make it 'normal', he would have to abandon said rules and live a little. He had given in to a temptation that had been there, hiding inside, for so long. It was only now, looking back, that the Doctor could see the foolish nature of his mistake.
His life had lacked the intimacy that any sentient life form would be proud to call their reason to live. The only option available to him had been in the befriending of his companions and granting them the whole of time and space, no questions asked. Who would be able to resist? The Doctor knew that he had not been able to.
He now realised that he had been wrong. It had been his decision to distance himself from his companions. The Time War had only reaffirmed that belief. When a man became too close to someone, it only made him more vulnerable to pain when they became lost or distant. Despite the knowledge that his lack of intimacy had been his own decision many lives before, in his last life, when it had been his last life and he was embroiled in the mystery of this impossible girl, had he allowed himself to slip into habits he had not practised since his life back on Gallifrey.
He would allow himself to kiss her forehead and hold onto hugs for a few seconds longer than he should have done. They were intimate. They were together in almost every sense. Unbeknownst to himself, the Doctor had let his guard slip and left not only himself open for injury but also those his rules were meant to protect.
This change had made him realise the impact of his mistakes. Clara's reaction to regeneration had not been what the Doctor had expected for someone who knew about regeneration and had met, even been kissed albeit on the hand, by one of his past selves. He expected her to be wary and a little frightened but not to the extent that has washed over her since Trenzalore. Clara's reaction was in response to the realisation that the flirty young man she had grown accustomed to would never be coming back. She refused to believe that the close friendship was gone. Like someone you become close to who suddenly drifts away, not because anything bad happened but time just sent your paths different ways, and you recollect the times you spent together and wished you could be back in them. Clara wished she could be back running with her silly Doctor.
He knew that this man could never be what Clara wanted even if the Doctor had still felt the same way. He'd seen the face in the mirror. It wasn't a kind face, not at first, not until you got to know it, to see it smile and laugh. The truth was that he didn't see Clara as she had once been. She was a different person to him now. They had both changed and it was to be seen how much that would affect their friendship. The Doctor waited for her response. He needed her to understand the predicament he had placed them in and that he didn't blame her for it.
'I never thought you were.' She replied.
'I never said it was your mistake.' He turned away from his companion, knowing that she understood. He took full responsibility for the pain she had been through because it was the right thing to do and from now on the Doctor would endeavour to right the wrongs of the last 2000 years. No matter what it took.