A karmic contract doesn't just have to be between lovers, it can be between any relationship including, parents, siblings, friends, and even leaders who manipulate and try to control you.
When a karmic contract is over it is because one or both have learned the lesson of where they gave away their power instead of seeing that power always resided within and they never needed to look outside themselves for validation by anybody.
Once this is learned the contract is over because you will see the other for the truth of what they brought to your reality and finally see the lack within them.
This gifts you the power to say no more and stand up for yourself as a whole person.
This is how we move the story into creating more of what we want instead of looking to others to create it for us, which would only ever create more of what they want, not for you.