For as long as you can remember you've been putting one foot in front of the other. Occasionally along the way you've stumbled but ultimately you can't help but move forward, as the passage of time demands. You can never beat it - even in death, when gravity buries you deep; the earth isn't frugal with it's centrifugal and you will feel forever that the sky is made of quicksand.
But before all that becomes obvious to you, it's one foot in front of the other, like I said. Throughout many days and nights of walking you'll come to know stop signs and roadblocks and flickering street lights; sharp turns and cul-de-sacs and roadkill; breathtaking lookouts and vaguely helpful information booths. One day you'll arrive at a confounding fork and two brothers will be waiting patiently for your arrival.
One always lies and one always tells the truth, but you don't know which one is which. One fork leads to happiness, the other to despair, and you must find out which to take, but can only use one question to do so. What same question can you ask either brother to continue on to happiness?
First one to guess correctly gets a lollipop and some free bad advice.