Unfortunately there will always be those breakups that remain as such, and really, many of those really are best that way when we take a long-term view of the situation.
Time really is a great healer — ish. That is, as more and more time passes by, more and more life has been experienced. And that often tends to help rub away the marks left by the relationship.
Us humans are excellent at living in the past. And so we can carry forward those feelings from the past, mainly those unresolved, keeping them fresh in our present time. Not great.
It's important to realise this.
How much you do this and how deep the issues determines how well the "time is a great healer" thing pans out.
If your relationship was not salvageable, if you've given it your best shot and think it is time to move on .. you probably would like help to do just that. To move on.
I think this coping with a breakup article is a solid place to start. It covers quite a bit of ground.
Here's another you might find useful.
I may write more on this in the future, but the above resources are decent to investigate in the mean time.
I wish you every success.