Well fellahs, the solootion is pretty thimple - and comparable to what a polite person does when exiting the WC after deposting some WCs (i.e. Water Closet and White Castles).
Light a match.
Or, more practically, light a candle (any candle will do - although I find a Vanilla scented votive really puts me in the mood). Or you can light one of the burners on your oven (not particularly effective if you have an electric range).
Try that and you will never cry while cutting onions again - unless you are also watching "Message in a Bottle". That movie soooo tugged at my little heart strings.