When I was a hairy arsed youth, doing my apprenticeship, I was told the following -
When you get married, get a big glass jar and put in by your bed.
During the first year of marriage, every time you get your leg over, put a dried pea in the jar,
In the second year, every time you get your leg over, take a pee out of the jar...
You can guarantee, by the time you die, your still taking dried peas out of the jar.