I actually have a longer Doctor Who thing on the boil, but this just popped into my mind whilst I was failing to do my homework. 100 words of angst on the theme of regeneration; equally applicable to either the Doctor or Captain Jack, I suppose.
It feels like dying. No, it is dying, every time, and the mortals who say how wonderful it must be to live your life again have only come to irritate him. He hates them for it, hates them and loves them and pities them all at once, because it's not the living that matters but the moment when it stops. And that moment is dark and terrible, no less death for the certainty of resurrection, and he doesn't just have to endure it once, but over and over and over again.
The end, when it comes, will be a relief.