If somebody’s trying to persuade a friend to go with them to a nightclub for some dancing, they might say “Carpe noctem!” — meaning that if there’s a chance to do something great at night, you should take it!
Carpe noctem literally means "seize the night" in Latin. It entered English as an imitation of the more common phrase carpe diem, meaning "seize the day." Carpe diem is often used to encourage people to grab hold of life by making the most of each day, taking every opportunity a day offers. Carpe noctem is used a bit humorously to focus on the same attitude towards nighttime activities, particularly the fun ones.