There comes a point after an ending when you have to change your mind, or at least your mindset. We forget that our brain and emotions are not spoiled toddlers high on sugar. No. We actually have control over them.
There's a bit of martyrdom that comes after a breakup. Emotionally, you are the equivalent of being shrouded in black. A gloom cloud hovers over you. Stock in Kleenex goes through the roof. For a time, you are supposed to feel pretty cruddy. But, sometimes, the crud sticks. We've all seen those relationship "widows" running around. "How long ago did they breakup?" "A year ago." "Oh. Wow. How sad." Not sad that she's still bummed over the breakup, but sad she's still not over it.
We can decide to feel better. Sometimes you have to decide that every thirty seconds. But, once you start deciding to feel better, it will start to actually happen. You'll need to remind yourself less and less.
I'm not talking about burying your feelings. That's not healthy. If your sad feelings keep bubbling up, it's been a while after the ending, and it's a little more than just your breakup making you feel blue, you might want to talk to someone. And I'm not being snarky about that. Really. If you are in emotional pain and it's not easing up, see a therapist, counsellor or member of the clergy to help you through it. But, if you are in the habit of thinking about your relationship just to see if you are going to feel bad about it, then stop and decide change your mind to feel better.
Think I'm being harsh? Well, what's meaner: You letting yourself feel rotten or me suggesting you get over it? I just think you deserve better. Especially from yourself.