Anticipation

Anticipation is an emotion usually someone waiting for something. This can cause pleasure or anxiety depending on what the person is thinking of.
Anticipation can be seen as an act of sexual desire. 
Anticipation can be shown in many ways; for example, some people seem to smile uncontrollably during this period, while others look or feel sick. It is not uncommon for the brain to be so focused on an event, that the body is affected in such a way.