I always get tempted to take profit off the table as soon as I can make 3%. I have regretted many times after seeing how I got left behind if I had a bit more patience and had held onto my investments a bit longer.
Just remember the old saying .... "Sell with regret" If you feel like its the right time to take some (or all) of your profit off the table, then DO IT. You should always be looking for opportunities to take some profit, you never know when the market will turn. It is absolutely the wrong thing to think you should and then start looking for reasons not to. That's absolutely wrong. You should never dissuade yourself from taking profit. Finally, the shorter the timeframes you are trading, the more important the above statements !
I think this is different for everyone. It depends on how you trade. I try to take profit at profit targets or near them. If price sky rockets several days in a row I take profit. If weakness is building in the charts I take profits. At the upper edge of a trend line I take profits. If a longer term trend I am following looks like the trend is ending I take profits. And of course if I get stopped out for a profit or loss I get out.
Letting profits run is one of the biggest challenges in trading, and IMO the number one reason that so many traders fail to stay in the game. But you need to master it if you have any hope at all of long term success. The next time you're tempted to pull the trigger early, just get away from the screen and picture the larger view of what you're trying to accomplish. Avoid the impulse of enjoying a quick rush. Be a professional and think of the long term.
Losing missed profits is losing too. And it will influence your average win/average loss per trade in a negative way. If you take profits too early your profits will diminish but your risk and stops will stay the same. So, bad for trading. In an extreme case taking profits too early can wipe out your account.
Have a plan going in, if you find you are "leaving too much on the table", adjust the plan. Your exit strategy is part of your plan.
That's the main reason why many are never successful. They don't have this. You should also be able to calculate correctly the impact of every decision you take. What looks like a good idea, often is not.
If you do that, you will blow out your account. Small profits and big losses = ???? You MUST let your winners run. You dont do that = blow up.