Why does the break-up hurt so badly if we weren't even together for long time?

I had my eyes on him 7 months ago and there was a lot of flirting going on but we actually never met up. He was a customer at the casino I work at and saw him often. However, I got fed up with his games and he would always spark so much emotion and interest in me and suddenly leave without saying goodbye. He would interrupted me whenever I was talking to any attractive colleagues and flirt with me in front of everyone but he never asked me out. I got fed up so I asked to work in a different department of the casino so I don't see him anymore. I didn't see him for 3 months until I unexpectedly bumped into him a day before Christmas and i saw him sobbing that his flights got cancelled and he couldn't fly back home and he finally asked me out. That same night everything escalated and we started dating for a month, did so many things together and met each other friends and always spent time together. Until he decided to break up because he said I am too much for him and he just said he's not feeling it. He said I deserve much better and he can't be the guy I want him to be. How convenient, he flew to the Caribbean 3 days later with his male single friends and he's gonna stay there for a month. Anyway, I am having extremely difficult time accepting its over and that I might never see him again. I can't understand how can such short-term relationship have such strong impact on me? Have I developed feelings for him? How do I erase him from my life?
Why does the break-up hurt so badly if we weren't even together for long time?
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