I’m not particularly good at maintaining any personal boundaries (and I am not particularly convinced of the Christ-likeness of much of the notion of boundaries either), so this poem amuses me. It’s actually more about controlling your own thoughts, and what becomes of them in "winter snows", but I think you can apply it more broadly also (our external boundaries can topple over then also).
Red Deer in Snow, by Robert Chapman-Firth, from here.
My summer thoughts, meek hinds, keep their own ground.
They graze and drowse and never think to roam
Beyond the pale of what they think is home --
A landscape with one fence, and that for deer.
Yet though it’s seven feet high and so seems fit,
In winter snows they walk right over it.