A term used to describe someone who is in a very dangerous situation.
(i.e. If you were walking on a giant razor's edge and fuck up, you either plumet to your death or you slip and land on the razor...getting chopped the fuck up and then raining down below).
A saying reputed to be of around WWII era.
Said to a person when they're busy wasting their time running their mouth off complaining over a usually trivial matter.
Meaning:
Much like a child pouts their lower lip when they're not getting their way, "Walking on your lower lip" implies their lip is so far pouted, they risk tripping over it.
"Life is so hard, I can never get ahead, everyone is against me, I'm not popular, and it's all the government's fault"
"Bah, stop walking on your lower lip and do something useful".