Original saying was "I'm all
right Jack, pull up the ladder".
Meaning when a man had got safely on board ship by climbing the ladder from the sea or from a lifeboat,
don't bother about saving the rest of the guys because I don't really care about them.
A thoughtless self-serving
person when asked to sympathise or
help someone who had lost his/her job might say "Well, I'm all right
Jack!".