don't beat yourself up, plenty of us have been caught out despite being so careful with management.
Acorn used to get depressed if kept in, we can't keep him in even if he has a lammi episode (complications left over from his first attack) so he goes out during the day and in at night - I half sanded his little paddock which reduced the ammout of grass he could get at - I can eleminate it altogether
but found giving him a small bit kept him interested but not enough to cause a problem as his main diet was hay, his was winter lammi so did not have the issues of growing fresh shoots and the problems that brings, grass does not seem too much of an issue for Acorn as a trigger but we restrict anyway for weight which obviously would not help. Depression in itself can be a trigger and certainly can hinder recovery - Acorns not big enough to try getting out over stable doors but Charlie is - we have an anti weave grill in which means if he has to be in he can look out but not get out - my neighbour uses a stable stall guard on the top section of hers which seems to work but again can't get head over so she put a window space in the back big enough for
him to look out .
I do feel for you the first week is always the worst IMO for both of you, have you an area non grass that could turn out in - or has vet insisted on box rest and no turnout or just no grass?
Do hope all goes well for you both