move on (emotionally)
I mean this in the emotional sense of
'You need to move on'
'I can't move on, I can't stop thinking about him'
Why don't you use "seguir para adelante".
"You need to move on" - "Necesitas seguir para adelante."
I can't move on; I can't stop thinking about him" - "No puedo seguir para adelante; no puedo dejar de pensar en él."
I hope this helps.