I think there are grudges over silly trivial matters and it is silly, trivial and may even be pathological to hang on to them and go over and over them.
I think there are also deeply painful and distressing wounds that linger and, possibly, continue but are described in a kind of shorthand by a single anecdote of some hurtful moment. I wonder, for example, if the wetting the baby's head mentioned, I think, by Ana could be shorthand for a long-standing feeling of being disregarded and dismissed by the baby's father.
Ana It was just a good example to use as I know of a long-standing problem where a similar story is the exemplar for the greater issue.