The First Doctor seemed like the type to fight regeneration - it actually surprised me that Twelve is the same. When they shot that very first regeneration scene, did they even have a name of it yet (regeneration) because I love the idea of the doctor refusing the loose his first face, his identity but then every incarnation since has embraced the act of regeneration even if they didn't want to change. Twelve really seems adamant about dying rather than regenerating though.
They didn't actually name it, or even present it as a consistent phenomenon, until the third regeneration.
The first regeneration (Hartnell to Troughton) was called "change and renewal", because he was getting too old. It was established as a function of the TARDIS, I suppose de-ageing him when he would have otherwise died of old age.
The second regeneration was established as the Time Lords changing his appearance as part of his punishment, along with exile on Earth. He had the choice of a number of faces and said no to them all, so one got picked for him. He was
very against the whole thing.
It was only during the third regeneration that it was actually named, and they always treated it as one incarnation coming to terms with his death and bowing out. They even poked fun at it during Romana's regeneration, when she treated it like trying on bodies in a dressing room before settling on one.
Then in nuWho, regenerations started getting violent (with the energy spray) and the Doctor started being resistant to the process instead of accepting it.
(I imagine the Sixth Doctor would have also strongly resisted regeneration, had Colin Baker come back for the scene.)