It burst forth from his skin, through the sleeves of his jacket and out the neckline. It circled around him so that all he could see was the hot golden light. It passed through his mind quickly, his entire life as his eleventh generation, but also appeared to him as very slow. Every second hurt, clinging onto the old memories, more than he could say.
He saw Amy's precious face. Her long, Scottish, red hair fell around her, beautiful as always. Her spotted freckles and bright smile filled his mind for most of it. Her and Rory jumped together, a leap of faith, to survive then disappear again. Why couldn't he have held onto her tighter? Why did he let her go? The apology he wanted to repeat tore him apart "I'm sorry for making you wait."
River's crazy blonde curls and wacky mannerisms are what he thought of next. He saw her hands around the blue notebook, saw her lips curl into a wicked smile as she warned him of spoilers. He loved and lost her as well.
Then Clara, sweet Clara, she was his impossible girl. There was no one as clever as she was, lifetime after lifetime she was clever. He adored her like all his other friends, her loveliness and brilliance astounded him. So many amazing things in the universe and still every individual person astounded him.
The Doctor felt like crying, why was this happening to him again? The dread of turning into another person was unbearable. There was chance he'd be a person to which his own fond memories meant nothing to. All the heartache from his last regeneration arose again, remembering the time he split from Rose, Martha, and Donna. How many people had he left behind? How many people would he disappoint in his next life?" He felt himself becoming another body, one that felt strange in his clothes, one that didn't fit quite right. I hope I'm ginger. Thought the twelfth doctor, he had regenerated.