On a day like today, when the markets have moved against the prevailing trend, there can be a temptation to give existing positions an extra bit of leeway, should they have also fallen back. Some may have actually gone through pre-determined stop levels. It is critical to your long-term success that you adhere to those stops, take your profits, and move onto the next trade. Who's to say that a one day 'blip' may be the start of a trend reversal?
Trend following is simply playing the probabilities - some traders like to think they have a crystal ball, and try to predict what will happen. Remember the wise words of Lao Tzu:
Those who have knowledge, don't predict. Those who predict, don't have knowledge.
Providing that your basic methodology has a positive expectancy, strong risk control and a belief in the signals (entries AND exits) that your system is giving you will lead to longevity and profits in this game. After all, you created those rules or parameters - if you override them, then what was the point of spending all that time and effort creating those rules?
In the words of Kenny Rogers and The Gambler:
"You got to know when to hold 'em, know when to fold 'em,
Know when to walk away and know when to run.
You never count your money when you're sittin' at the table.
There'll be time enough for countin' when the dealin's done."
No matter how good the charts have looked for a while, when the party is over, don't overstay your welcome. Exit and move on.