Do you see (spiritual) surrender as an act of choice or is it something that just spontaneously happens?
I don't see it as a choice or decision, not even an intention, although these may all be good starting points that predispose a lightning strike from grace's realms.
Predisposing means encouraging a meeting point of sorts?
Maybe that's what the phrase 'wearing your heart on your sleeve' indicates; a meeting at the point that higher spiritual influences touch us.
Instead of an ego-mind shell that deflects or ignores these influences, creating a 'water off of a duck's back' effect, to coin another phrase.
Right, then there's opportunity lost, no real contact. But if incoming grace is met at the door its influence can be carried to the core of our conditioned mind, can lighten its load, can subvert its tyrannies.