Jim is trying to express to Huck that no matter what situation Huck is in he will grow from that experience and learn how to correctly place himself him culture and society and in doing so will create a environment that will be more suited to him. But this setting will crumble just like any environment that you are surrounded by. In saying this he is telling Huck that in order to live life to the fullest he must go with the flow and accept the environment around him in order to truly experience life in the fullest.
