I never take off full length when an intersection take-off is perfectly acceptable- I've got a schedule to keep, so runway behind me is completely useless- I don't want it anyway, thankyou. When I fly, altitude above me is useless- totally useless unless I only want it because some other mother is blocking me from climbing. Other than that, you can keep it, ta v much. Fuel still in the bowser is useless- because I've always had enough. Ain't never come near running out yet- my job is to make sure that doesn't happen.
All in all, yet another trite (alleged) saying passed from mouth to mouth by simpletons that means absolutely nothing, and is destined to waste our time ad infinitum. Is there any way we can put a stop to people spreading this daftness? Like exterminate the culprit everytime? It would die out in a generation.