how to move on

it’s been five and a half months since my first love and i split. i know everyone says to just move on. easier said than done. how do you move on when all you can remember are good memories and laughter and smiles and then suddenly all of that is just gone one day? I miss him still almost everyday and I feel stupid. I get it, I should move on, BUT HOW? I can’t date. I’ve tried and just ended up leading people on because the breakup left me with unresolved issues and my self esteem has plummeted. How do I forget about him?! I just feel like I lost someone so important and meaningful to me and it hurts everyday still and I feel dumb and weak.