I think that bitcoin will fall to zero if there is not a single person to accept bitcoin and as we see bitcoin is regularly pumping and no one can deny its success.

The very easy way to not sad when bitcoin become to zero is that whenever you achieve profit then remove your profit and save it with yourself and the remaining amount which you initially used for bitcoin investment will still be used as investment so whenever this happens you will have take your profit so there will be no need of regret in bitcoin.