Answer for Have you face situation where you thought the company you bought was a good one, but few year later it's ROE start to degrade year by year. If sell the stock you lose money, do you wait or sell?

Yes, this may happen. That is why, when we buy a company, we have to factor in margin of safety. However, I would not sell if the company’s intrinsic value is still above its price. I would sell the stock only if I believe that the economics of the business has permanently changed and that company’s ROE will not recover back to above 15%. Moreover, I must be able to find a better opportunity to employ my funds should I sell of my holdings.