"Good fences make good neighbors."
A relationship that gives everything and shifts to soothe every whim offers nothing to push against: no boundary, no footing, all padding.
The steadfast fortress, unable to give us all we want, does two things: it gives us something stable to challenge, and it keeps a mystery intact.
Our struggle against it (around it) shapes us, while easy fulfillment produces porosity: a total acceptance with no boundaries.