I never leave town without at least one of these in the backpack. I have two. If not for myself, perhaps for another biker stranded for the same reason. It only takes a US quart (887 ml), which is plenty when you are dry. I also have larger fuel canisters, but they need to go in a saddlebag or locked on a pannier's back.
Experience is the culmination of your own scr3w-ups and those of others that you were fortunate enough to hear about before repeating them yourself.