You are right, if we don't sell it then still we are not yet losing something because the investment is still there and we cannot assume already that when the price gets low that we are already lose, it is not calculated like that losing starts the time we sold our investment.
It is just like a gambling that is correct, but in trading there is likely more chance of winning because you can earn here as much as you can, by just having enough patience and trust in what coins you are trading at, unlike in gambling that you only left with two options and that is to win or lose.