Power is a complex thing. Sometimes enabling the dysfunction of others is a kind of power-play in and of itself. I don't want to explore that too much here and make the waters muddy though.
But be clear that I'm not saying this choice to pull power back is inherently bad. In fact, it's downright necessary at times. The point merely remains that YOU are making a choice, not that the other individual MADE you make a choice.
When you speak of boundaries, I hear that. I too have spent countless hours supporting people who don't necessarily appear to appreciate the gift I've given them. I've unwittingly enabled people to be clingy and needy. But I OWN that, those were / these are my choices, I choose to listen and at any time I could assert my own independence in the matter and gracefully detach myself. It has everything to do with me. Does that distinction help illustrate what I am trying to convey?