Science.

Murphy's Third Law of Fluid Dynamics

No matter how many times you lift, carry, or balance a five-gallon bucket of water when it is eighty degrees outside, it will not spill. At most, a fumble will deposit .0001% of its volume on your shoe.

No matter how carefully you lift, carry, and balance a five-gallon bucket of water when it is thirty degrees outside, it will spill. At minimum, a fumble will deposit 15% of its volume on your pants.

Thanks, Murphy.