How to focus? I daydream too much?

I find myself daydreaming all the time. I try to dom something important and I lose focus quickly because I start to think about something random, like some random hypothetical thought about the future. Like, I would think about me n my brother fighting or me n my gf going out or something and I'm acting out the whole scenario in my head.This happens all the times out the day and its holding me back from me being in tip top shape mentaLly. What should I do? And I don't want to take any meds (unless they're natural)