Never think that you've wasted months or years in a relationship or a job or some other situation that didn't turn out the way you had hoped. You are always exactly where you are supposed to be. No experience is ever wasted.
My son got married a few weeks ago. However, what should have been a weekend of unadulterated delight was filled with moments of sadness. Not because I don't like his new wife or because I'm estranged from my son -- no, I was unhappy because my ex-husband invited his girlfriend.
Your letter is not about your ex being a d*ck. If he were a d*ck, you would have stopped thinking about him by now. But you are thinking about him. Almost a year later, and you're reaching out to me, too. You said you shouldn't be thinking about him though. Has someone told you that? Often our friends do.
I felt like I'd been punched in the gut. The body-numbing, time-stopping, paralyzing feeling of hearing your spouse say they are no longer in love with you. It seemed my worst fears had come true; he'd fallen in love with someone else and wanted a divorce.
Life does that, it patiently waits for you to catch up with it, always reminding us that it is also short. There may not always be a tomorrow. Stop saying I will do that when.... Or I will be better when... start living your life. Don't make life wait patiently on you.
Consider this a litmus test for moving on. ✔️