Not apathy—but a deep appreciation for the feelings, thoughts, and experiences that come and go, without needing or desiring anything.
For instance, love—you can feel genuine, unconditional love for somebody and still be detached from the outcome of anything manifesting from that feeling in reality. You transmute the energy of love into a creative act: writing poetry, photography, etc.—and you find power in that.
Or anger—you transmute that energy into pure vitality and physical power.
And of course, validation—letting go of external praise or even hate is pure power, in the sense that you are no longer doing anything for an outcome. You do something purely for the love of doing it.