I Need relationship advise with me and my boyfriend who was my ex?

Ive known Nic since first grade and he was my first little boyfriend crush in 5 grade and we officially started dating junior year of high school. We dated for exactly a year when he suddenly broke up with me on our one year anniversery totally out of the blue, no warning, nothing. But i know its sometimes what guys do they get nervous about getting serious or they see their friends having random hook ups and they want that too...So 6 months later we got back together and everything seems different, better, way better!!! But the break up still hurts me. I still tink about it and it still stings and makes me cry...is that bad? How can I let it go...should i let him go? Please help me!!!