Sometimes, thinking they will come back can motivate you
I know, it's something everyone advices against, but often we feel so emotionally drained after a breakup, that we don't have energy to do anything at all.
Frequently we lose appetite from the breakup, and it can be a good thing for someone who wants to lose weight, but not for someone who is already underweight.
Often breakups motivate us to change our lives, because let's be honest, if we were dumped and didn't take it lightly, it means that we were too dependent on the other person. Breakup is a great reason to address areas where you are lacking.
In my case, it's the extreme need for validation and emotional support from others, and career insecurities. I became too emotionally reliant on my partner, and it drove him away. Sure, it wasn't all my fault, but I can see how my relationship patterns are repeating in every relationship and are killing it.
Anyway, there is always this background thought and hope they will come back, so instead of fighting it, it's a good idea to channel it as a motivation to change and grow.
Sure, they will come back, but only if I become a better person. They will come back, but I need to stop being dependent on them. They will come back, but I need to cultivate inner strength and discipline to achieve my goals.
And you know what is very likely to happen?
After you grow and heal, and improve areas of your life that need improvement, bring back balance, stability and resilience, you realize you don't need your ex. Then you can finally reject them, yourself. And it will feel awesome.