I see one problem with that dream that if we think logically even if you stay alive indefinitely if you do not have lower half you are not much useful for sex and you cannot even move around by yourself being only good as decoration.

on the other hand, process of cutting or destroying your lower half in some way may be interesting (except that when everything is finished you are just a lump of meat.)

So I wonder what fantasies on that matter you have yourself. being cut in half of matter of few seconds. and then what?
In your fantasy, do you feel what is going with your detached half like can you fell or even get orgasm if someone has sex with it?