Is there a rule?

Is there a rule that at the moment you most need to stop, your brake cable will break? (That's phonetically ironic.)

Is there a rule that when you start making enough money to buy moped parts you won't have enough time to work on mopeds?

Is there a rule that youth will always fade, pride comes before the fall, and pretty bikes will one day be scorned as "ratty bikes"?

Is there a rule that a deluge of carburetors will surely bring a dearth of intakes?

What's the deal with that?