It is a sin to follow your horoscope because only God knows the future and He won't tell us. Also, we can tell horoscopes are false because according to astrology, Christ would have been a Capricorn, and Capricorn people are cold, ambitious and attracted to Scorpio and Virgo, and we know that Christ was warm, loving, and not attracted to anybody.

Sister Mary Ignatius explains it all for you ; The actor's nightmare: two one-act plays (ed. 1981)