A good friend and I were talking about grief the other day and one of the things we agreed was that a key consequence of grief is "expect some of your key relationships to fail". As we both said we are not sure that you can know this during and not sure how much it's helpful to say it to people in the midst of the intensity of early stages of grief but we both reckon it's a profoundly true statement, as we have watched others and experienced significant grief ourselves. Certainly for us it helps us to just relax a bit at least looking back - and to be easier on ourselves than we otherwise might.
As I think about it, I reckon it's broader than just grief - I'd say that in any big thing in your life, whether good or bad, that's one of the things I'd say "expect some of your key relationships to fail". Not sure I like the word "fail" - but you get the gist of what I mean - "not be able to cope with it". That's certainly been my experience of all sorts of stage in my life.