When investing in stocks, should I buy all sectors or just a few sectors?

A common problem among novices is that it seems to diversify risks, but it is not enough. Buying one stock in each of two or three sectors is a lot. Retail investors have limited energy and skills and cannot focus on it. Since you have stocks in so many sectors, you might as well sell some of them. If you have enough risk tolerance, continue to chase hot spots and sell out those that are currently stagnant. On the contrary, sell the theme stocks and concentrate on holding relatively sluggish banks, real estate and the like. You can also combine the two, but don't spread it too thinly. Concentrate it on two or three stocks to facilitate management.