The Girl in the Fireplace - S2-E7
Doctor: I think we just found the hole. Must be a spatio-temporal hyperlink.
Mickey: What's that?
Doctor: No idea. Just made it up. Didn't wanna say 'magic door'.
The Girl in the Fireplace - S2-E7
The Doctor: Who are you?
King: I'm the King of France!
The Doctor: Yeah? Well, I'm the Lord of Time.
The Girl in the Fireplace - S2-E7
Rose: Are you okay?
Reinette: No. I'm very afraid. But you and I both know, don't we, Rose? The Doctor is worth the monsters.
Chosen answer: 1) When Stephen Moffat took over he ignored a lot of what had been developed before (there is not in-universe answer). 2) It would have killed Rose, so the Doctor absorbed the energy. His body regenerated before the energy could do a significant amount of damage that would prevent regeneration.