That was the last thing that my father told me when he took me to college for the first time, right before he jumped into the car and drove off into the sunset. My dad was a man of few words but he always had sage advice that made sense. This is a perfect example and it led to this little ditty:
The problem with copulation
Is the risk of increased population.
Dear old dad always said
Get head instead
And take the risk out of ejaculation!