Regardless of sex, we heterosexuals are attracted to good-looking people of the opposite gender. Once this immediate attraction is consumed (through sex), if there is nothing to hold one's interest, the affair remains a one-night stand. Thus, getting good at chess will only help you keep a girl.
If you want to get a girl in the first place, go to the gym, get laser eye surgery, grow a few inches, etc. which will make you attractive. Then, once you have satisfied your prey in the sack, take out the chessboard and say, "You think my **** was large? Wait 'til you see my chess rating!"
If the girl runs away screaming, you didn't want to keep her anyway.
Then share.