Losing a girlfriend sucks, and it can feel like you'll be forever alone. However, this is far from true. Consider this, at some point before this relationship, you were single. We can assume that the difference in the number of availible (not crazy, sick, or hurtful) girls is negligible between then and now. Since that is the case, there is no reason that you cannot get another girlfriend because you haven't had a mental breakdown and there are plenty available.
However, as other posters have mentioned, a relationship is a great deal of work. You're still a kid, don't rush into things- it's hard to go back. I certainly miss being a little kid, so I've decided to enjoy myself while this period of my life lasts (while still preparing for the future, of course). Sure, I'll fool around with girls, but I know it's just that, fooling around. Once I realized that, it became much less stressful.
To conclude, just have fun, stop worrying if you get a breakup. Imagine if you fell into a depression every time you fell off your bike as a kid- you'd never learn to ride it. So if you break up with a girl, don't sweat it. As long as nobody got hurt, it was all in good fun. That's what relationships at this age should be: fun.
-Penguin
