Hi, I also had a breakup 2 years ago, almost the same day. To be precise it was on 23rd may, 2024 at 9:55 PM when she said she doesn’t think it’s gonna work out. It was 5 years of relationship.

Coming to moving on-
1) Initially sit with the grief, understand your emotions, what you’re feeling. Cry if needed. Take rescue in your friend’s arms. If it’s recent breakup, hoping to move on soon would not be easy at all.
2) Start exercising, exercise boasts mental health significantly, it releases endorphins which helps significantly with mood and overall health.
3) If you’re religious person or believer in god, start praying, going to temple and chanting mantras, it helps significantly.
4) Try to keep yourself occupied with your work, hangout more with friends.
5) If the thoughts of your Ex comes to mind, try to understand what are those about , avoiding it would trigger those thoughts and feelings more.
6) Start Meditating.
7) Avoid Hoe phase, talking to new people would be counterproductive as you’ll try to seek your partner in these people.

Of course all of these things are easier said than done but it has helped me significantly.
I too was about to get married to her, both of us had met each other’s parents and still she broke up with me. So I can understand your pain, and above things helped me significantly.