Because

Lily made a very valid point today when I was texting her.
I asked if she missed him.
Her response?
Of course I miss him! He's my ex. The first person I fell in love with and he's just gone. I'll always have a soft spot for him.

Somehow, that explanation made sense to me.
I finally understand why I can't let go of Kip.
It's not that I haven't let go, which I have.
It's just that I'll always have a special part in my heart reserved for him,
because he was my first love.
He was that guy.