forgetting someone is tricky if you have a functioning brain but moving on is more than doable! allow yourself to grieve the end of the relationship, take proper care, and lean into your support network if you have one. Friends family therapy etc. Hobbies and structure will keep you progressing your life. Be gentle with yourself
Don’t forget, just move on from them. Mostly just time and working on the mindset change to understand that it’s ok and probably for the best. Like it wasn’t meant to be with that person and that what you had was beautiful, and it’s ok that it’s over, because having it is better than most people ever get. Everybody you date will end up as your ex girlfriend, it’s just whether or not it’s because you got married. And when you get married you aren’t going to be sitting thinking about her
From a neuroscience standpoint: stop doing absolutely anything that makes you think of them. Permanently get rid of any pictures, videos, texts, gifts, EVERYTHING related to them. Stop going to places you frequented together if you need to. Tell your friends to never mention them ever again. The less you recall the memories associated with them, the more synaptic pruning your brain does, and the more you forget them. If it’s something you can’t avoid, make new memories related to it instead