As he plummeted from the ship and towards a glass ceiling which might've been strong enough to repel him, he flashed back to his fourth regeneration which had taken place after he'd fallen from a much shorter height and thought Well, this was stupid...

It seemed like a good idea at the time, back when the ship had been doing a flyby over the manor. He'd remembered falling from a greater height without assistance on the way down during the Time War and surviving. He'd just...broken...both...legs back then. And, with him sorta being lucky number twelve because the him he didn't like to think about and the aborted regeneration which entirely skewed the count had actually happened...

When he'd crashed through the glass ceiling rather than bouncing off of it, breaking every bone in his body, and possibly regenerating into or finding himself suddenly looking at an asshole who was concerned with getting his Sixth self's remaining lives that could've possibly formed out of him if a large enough chunk broke off, there had been no time to think about the landing. As the pain of hitting the floor and quite possibly rupturing something vital began to fade, the only thought that was running through his head was How the hell am I still alive? Then his mind began to clear and turned to the Master, the other Time Lords and the fact that Earth was being knocked out of its orbit and into a new orbit around Gallifrey which was about to rather cataclysmically acquire two new moons.

Miraculously, he found himself able to stand despite the incredible pain he was in and he briefly wondered if what the Sisterhood of Karn had done to him had something to do with it. His regenerations since the Mistake had all been strange and far more violent than he remembered his earlier regenerations being, but then again, so had the circumstances behind them. Except maybe the being shot by the Dalek. Being shot by a Dalek didn't quite compare to regenerating after drinking a potion given to him by the Sisterhood of Karn when he should be dead, ending the Time War, or practically swallowing the heart of the TARDIS.

Several minutes later, as he informed Wilf that he was regenerating and saw the guilt in the man's eyes, he found he couldn't swallow his pride and inform the man that the process had already begun before he had gone and absorbed all that radiation that was rattling around his system since there wasn't any convenient radioactive shoe receptacles nearby and it would take more than a shoe to deal with the amount of radiation he'd absorbed anyways.

Saying he'd died in an act of heroism that had involved a no-win situation and the absorption of a great deal of radiation sounded better than "I jumped out of a spaceship without a parachute".