Jesus would explain to His disciples that spiritual life hinges upon living in active dependence upon Himself. That is the fundamental lesson to learn because it is the fundamental sin of mankind – the independent path. Jesus says without Him we can do nothing. Nothing! But it is human nature to try and do something in ourselves. We call it freedom and liberty; blazing our own trail; making something happen. But the end result is death and destruction.
The fall of man illustrates a fundamental truth: that whenever Self is allowed to rule in the place of Christ, the result is sin, sorrow, separation and death. Apart from Him we really can do nothing.