The clock is the measurement for the last time an individual has had sex. When a person has not had sex in a while (which is relative depending on the person) their clock needs to be reset. If they fail to reset the clock, it is possible they will go crazy and do something they'll regret. In conclusion, it is important to reset the clock every so often to maintain sanity.

Note: In order to reset the clock, some individuals may consider oral sex or heavy fondling as acceptable. I personally do not.

When you're being horny (especially around friends) and as a result shame ensues.