Ever go all in
and have a positive result?
You should never go all in if you ask me because the price can always rise again after you have sold so that would mean that you would miss out on some money.
Sell some and save some that is how you keep maintaining the cycle.
i like this idea so you are in a win and win situation if the you lose you still have the other part you have another portion to try it again just for precaution.
But, I believe he will be enforced to bet with other portion too as gambling will not let anyone to escape. Moreover, due to gambling addiction he will keep on playing more money from other sources like getting through loans. That is what happening with most of the gamblers. With or without conscious gamblers bet all their money in gambling. Very dangerous to any gambler.