It is some kind of strategy, mostly copied from buffet.
If I want to hold 100, I will buy 200 first. If it goes up 10% or 20%, then I sell 100 stocks, keep the 100 forever.
If it goes down 5% or 10%, buy again 100, hold until it comes back to original price or above 10%, sell the original 200 take profit
Sample I provide, but may vary different situation, or case to case.
Ultimate Aim is to make profit and see our investment grows bigger. Once the investment reaches 25% or above, I do not prefer to sell. If Stocks fall suddenly, they do not fall more than 25% in single day, still I can come out of market with positive gains.