Sooner or later your chain will fall off the front sprockets while you’re riding. On most bikes, to get it back on, all you have to do is shift it on by moving the left shift lever as if you were shifting onto a bigger chain ring. Pedal lightly and finesse the chain back into place. This will spare your hands a serious dose of chain grease. If the chain drops when you’re climbing, head downhill for a bit, shift the chain back on and turn back.