Time passes before past relationships cease to be ill and completely become the past, that is, a memory.
Many experts agree that only after this it makes sense to enter into a relationship with another person.
Otherwise, we will have to do double work: at the same time to complete past relationships and build new ones.
Thoughts about whether to call or not to call the former (her), especially if they persistently repeat, mean exactly this: the relationship has not yet been completed to the end