Why does this happen to me?

I meet a great guy...we start dating. I had a life before him...hanging out with friends and such. He had a life before me as well - not a problem for me. He slowly starts picking away at my life to the point that I have nothing left of my life and I am now submerged in his...feeling desperate, needy, and clingy. He breaks up with me stating that I am insecure. Why do guys want us to give up our lives for them but they do not do the same for us?