Asking for a break in the relationship?

This guy and I have been casually dating for about 6 months. I know what you're thinking.. "isn't that a little long to still be dating?" A few weeks ago, the guy had reinstated that we were only "casually dating."

The "relationship" has gotten a little routine and stagnant.. I only see him a day or two on weekends and that's about it. I still like him a lot, but I feel I need a break from it to clear my head and focus on other things- ("relationship" has been a bit of an emotional rollercoaster).

I've tried to ask for a break before (in person), but he ended up talking me out of it, and seeing him only made it harder to do.

What are your opinions on this- Do you think it will be okay if I told him over the phone that I want a break for maybe a few months? I seriously think that if I see him, I will end up not doing it.