How you manage the end of a relationship with your Gf without being Sad?

I also agree with Zenith. You're gonna be sad irregardless, especially if there was a lot of time and emotional effort put into it.

It's cool to be sad about it, just don't let it ruin your lifestyle and drag on forever. I'm guessing you're young so something to always remember that is there a literally millions of other girls to meet and fall for, as cliche as it sounds. You'll know when you find the one.