Interesting, this is the same for myself. My longest relationship was one month, then I became bored and broke up with her, same with most girls I only find somewhat attractive, as soon as I actually sleep with them it's boring and I don't care much any more, but the build up to it is the only thing that keeps me engaged.
Also the same in regards to most sports, basketball I was good but became bored, hence why I started martial arts as I'm always improving..
I'm interested to see what some of the replies to this are
