It hurt. It hurt worse than everything she could remember experiencing. It was like biting into hot metal, like her bones were burning while still inside her body. But it left no lasting physical harm, and even the mental one was all things considered contained. Yes, it strained her, and yes, pain was not a good thing, but by its own nature it did not harm her as much as something equivalent to it would have. It did not leave her as traumatised as it could have. It was almost dreamlike in a way, something that wasn't really there after it was left despite how real it felt in the moment, something her body forgot. She did not like living through it, but she knew it wouldn't remain, so she pushed herself again.
It was, in some twisted ways, deeply fascinating. Had she been an external observer to her own happenings, something not too far from how she felt at times when the pain and her conditions pushed her to the brink, she would have been utterly enraptured with the process of change that had led her there, and even with just those rare moments she was still rather interested in it. In part so because understanding how things were happening could help her with what would come next. While she didn't have the time to entertain a purely academic interest in the subject, its potential utility was enough for her to consider exploring it further, or at the least paying better attention when the occasion presented itself and dedicating some reflection to it when allowed to.
It still hurt tremendously despite all that. She had never been stabbed with a knife, and she hoped things would stay that way, but she was still confident every action she took felt about the same as that would have. A far cry from how things had felt at the start, but in its own way that was good. She'd gone from drowning being her main concern to it being the act of wading through the waters itself. She'd been fighting, and it had started to fight back. That was good. Maybe it wasn't as self aware as that, maybe ascribing a decision like that to it wasn't right or wise, but it helped her. It helped with giving her a goal, if she thought of her adversary as a conscious force.
But that still could only take her so far, and she knew that too. The real personality in the way of her objective was her own. If she wished to succeed, she had her self to get through, and nothing else. What she was struggling against was only a tool, was supposed to only be one, and it was only a vehicle to highlight her own inner struggle. It being the cause of that struggle was irrelevant when she was set on gaining control. Her own self was the source of her pain as much as the reason she risked falling.