The phrase, "I'm gonna call it," is often used when no other seemingly legitimate excuse is available to the host. It is a method whereby the host can cancel the social activities in order to alot "alone" time for him/herself. These activities vary, but often include: Xbox, self-pleasuring, viewing pornography, and wasting time on the internet.
2.) "I know it's only eight-thirty, but I'm gonna call it so I can get up early and clean my room tomorrow."