1) Failing to book losses when the need of the hour was to book it and shift to something better. Then that extension of mistake was failing to sell my stock even knowing I have gotten a better one which should do way better than the holding one but still call it mental blockage or being scared to take a loss. You may love the stock but it ain't loving you back. You need to be ruthless in booking losses. Helps big time.I am absolutely ruthless in booking losses this days. That's discipline too which is a trait of a good investor.
2) Failing to buy a stock just coz it doubled or tripled recently or moved massively. You need to absolutely forget what happened earlier. Just focus on the business and it's potential,it's valuation and the prospects. Don't care about the price. Often it's the breakout which was only required to help it move in the next orbit. That's how multibagger emerges. They consolidate,move up and again consolidate only to move up again. Retail investors would always sell their winners to average their losers which is the worst possible sin.
3) Daily churning of portfolio. Another crime which deprives investors from achieving big wealth. Ones you have got hold of good strong agile promoters,thats it. Get laid for next 5-10 years. No need to go for new companies. You only gotta become rich once right? It's a tremendously difficult task in Indian markets to find good promoters with massive growth potential and at the same time which cares for the minority shareholders. The objective remain to grow your wealth at 26% cagr or double your money every 3 years. 10 lakh becomes 100cr in 30 years that way. What more could one desire? Your prefered stock may remain silent for 2 years and 360 days only to double in next 5 days to fullfill it's desired CAGR expectations.. That doesn't mean coz of boredom you will sell that and move to something else. Investing is boring and if it's looking exciting to you probably you are doing something wrong.