How to supress romantic fantasies?

I’m far from having a boyfriend but I can’t stop dreaming about being romantic with a guy I haven’t even met. There’s someone I realized lately that I like the idea of more than anything, so I tend to use him in my daydreams. I guess I’m an idealist, a romantic… and I get easily distracted. Sometimes I have to be a productive person and I just can’t….

I know I sound like a loser, but I’m asking this question seriously!

How do I focus on the present instead of something I don’t really have? (And something I feel like I will never have.)