A negative Neptune transit in your natal chart could get you hooked on drugs, alcohol, prescribed pain pills, gambling, or some other addictive vice. You could literally fade away in some way, or knowingly disappear from a life that no longer holds any meaning for you. You could fall into a coma from an accident. You could become a hermit, or recluse because you find the world too harsh or too  cruel. You could become a nun, monk, priest, minister, or rabbi or turn yourself over to a cult. All these things are ruled by Neptune.