The first time it happened, he didn't grumble too much because the universe was at stake. It bothered him, though, to think that the Time Lords could just steal him from his own timeline and drop him in that of his future self. How had they found him? And, more to the point, what were they going to do with him after he helped himself save the universe from Omega?
Well, whatever the answers, he couldn't do anything about his current situation save flow with it. And maybe saving the Time Lords would convince them that a little meddling never hurt anyone and they'd leave him alone. Yeah, if penguins could fly…
Still he told himself not to worry and got on with things. Like observing his (frankly irritating) future self. He didn't like the idea of becoming a dandy-not one jot. And especially not a dandy who apparently worked with or for the military! Although, having Brigadier Lethbridge-Stewart there comforted him somewhat. But he wondered why he was defending Earth from one time and place.
Also, something was wrong with the TARDIS. He could tell the minute he materialized inside her. He couldn't tell exactly what the problem was, but there was something off. And he suspected the old girl had been sitting in the corner of that laboratory for an inordinately long amount of time.
Even Jo bothered him. Oh he liked her of course, but her very existence as his future self's friend and companion was telling. The Doctor didn't like thinking about his future—and here he was confronted with a future utterly different from his current life! Working with UNIT, not traveling much if any, having Jo as an assistant, becoming a dandy mule-head…
Time would change him, he knew. But he didn't like to see how much.
He really didn't like to guess why, either.
The second time he met one of his future selves, he met two. What started off as a day of complaining about what UNIT's new head had done to his office quickly became a mad jaunt through the Death Zone. At first he hadn't known this was a paradox of clashing timelines, although when apparitions of Jamie and Zoe appeared and he recognized them as fakes based on them knowing him—which didn't make sense. He felt like he knew things he shouldn't, so he studiously ignored them.
But when he ran into selves one and three in the tower, and, more to the point, recognized three as the man he would turn into someday, he got suspicious. Had something like this happened before? Oh, yes, Omega! He hadn't remembered that incident until this moment. Obviously the Time Lords had wiped his memory.
He wondered how much else he didn't know he was forgetting.
He didn't mind meeting the other future self, the crickety one. Obviously this version was from some far future, one that he didn't have to worry about yet.
He knew as he exchanged verbal abuses with his next self while heading into the TARDIS that he would forget this too.
He always (how many times was always? Just twice or where there more times he couldn't remember?) argued with version three. It seemed a little silly, but they were so little like one another that it was inevitable. Next-him actually cared about appearances, and seemed to insist on talking down to people, and didn't like recorder music. And he looked almost graceful when running, which was more than a little unfair.
Besides, three reminded him that eventually everything, even the mad-cap dashing adventure that was his and Jamie's and Zoe's lives, would end.
The third (possibly third, almost certainly last) time was an accident. So much of an accident that his future self didn't remember it happening the first time around (for him—English was a language not designed for time travel). The only indication of the severity of the crossed timelines was him and Jamie gaining several decades of age in appearance. Jamie thought it was funny; the Doctor merely rolled his eyes and looked forward to a return to properly dark hair.
He wasn't bothered by this self or by the nice American girl he was traveling with—again, they were so far in the future that worry was pointless. He didn't really like the coat, and wasn't sure if he approved the fact that the majority of his future selves which he had met so far seemed to gravitate towards younger bodies. They lacked a certain gravitas, perhaps. He put this to himself and got a caustic 'oh and people take you seriously, do they?' in return.
He wondered why his future selves seemed to like him less the closer they got to him in order. He supposed, piecing together what little he was allowed or had fought to remember, that something had happened, perhaps, and they didn't like to be reminded of it.
He was getting an odd, sinking suspicion of what, exactly, had happened (the apparitions in Rassilon's Tower and the weird, half remembered, knowledge that came with them; the fact that the Time Lords had reached from his third self's timeline to get him and then had just let him go despite the laws he had broken).
He didn't really like to think about it.
"We'll have to forget this adventure, you know," he told Jamie after they'd left. "I-that is to say, he—didn't remember so I shall have to wipe it out of my mind, so to speak. Yours too. Don't worry, I'll make sure it doesn't hurt.."
"I thought Zoe said brains don't have feeling, once. Can loosing memories actually be painful?"
"If not done properly, yes. If don't right, you won't have the even vaguest inkling that you're forgetting a thing."
The Scot shrugged. "Well, alright, Doctor. If you're sure you know what you're doing."
The Doctor nodded and, placing his hands on his friend's temples, removed the necessary memories. Once he'd caught Jamie and safely lowered his unconscious form to the floor, he reached into his own mind.
For once, though he knew it was rather cowardly of him, he was glad to forget. He erased the last adventure, his suspicions about the future, made it so he could go one for however long he had left without worrying about what tomorrow would bring. Whatever would come would come, and he would meet it when it did.