Anyway, there is no 100% guarantee that you will make a profit in the long run; the only thing that motivates people to hold more Bitcoin is because of the cycle and historical data on Bitcoin.
If you know the bitcoin history on every cycle and understand block halving, you will think about buying more because the cycle may repeat just like what happened on every cycle.
That's the reason why investors are pushing themselves to buy more because they know after block halving or near block halving there's a big chance that the price will hype again, just like what happened in the past.
Investment contains risk but if people have proper management, and understand about the market well, they will reduce a lot of probability of selling bitcoin with loss, because if they can hold it longer, they will have profit. If they can avoid forced selling situations, they will not have loss.
It depends on each person time budget too, like philipma said some times that he is old, has limited times and he does not have too far plans for his Bitcoin portfolio than the younger people. Philipma makes a lot of posts so it's hard to find that post of him. The young, middle-aged and the old people have very different investment plans, the young can take more risk as they have a lot of time and chances to correct mistakes with second or further chances in the future. They can hold bitcoin longer than the elderly too because they elderly must think about their life quality in next years like one by one, not too far.
Selling your bitcoin because of the price is falling is not a good idea, many people lose their money because they sell their bitcoin with any price without thinking
Their thinking is useless if they did not have good financial, risk and capital management previously. Lack of proper financial, investment capital and risk management, they will have to fall into forced sell situations even they don't want to do that.
Think it is like if your pocket is empty, your bank account is empty, and what you have is only bitcoin, surely you will have to sell your coins even with negative ROI.