If, as you’re lowering yourself, there’s a problem and you need to go back up (damaged rope, or rope not long enough for example) fit a jammer to the rope above you with a double sling. Clip your long does-tail to the jammer so you have 2 points of contact. Step into the sling to stand up and at the same time pull the rope through your belay device. Sit into your belay device to move the jammer up and off you go.