How long do you hold on to past relationships?

How long do you hold on to past relationships?
At what point do you let go and really move on?
By this I mean stop following them, stop reading and commenting on their posts, stop trying to insert yourself into their lives, and basically, just give up and move on?
What do you consider to be an appropriate amount of time to hold on?
Have you ever held on longer than was probably healthy or maybe you have been on the receiving end of this?
Tell me your experiences!
(Feel free to comment anonymously if you wish)
How long do you hold on to past relationships?
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