Like brownsfan mentioned, it is psychologically easier when you have the luxury to scale out. Scaling out will also let you hold a last portion of your trade if you are absolutely convinced it will go higher after a pullback.
Make sure you also have warning signals that you like to spot out during a trade that will convince you to exit or book some profits as well. A few things that offer warning signals in my trades are:
- New TICK high/low
- ES, Sectors making lower highs/ higher lows
- TRIN range breaks
- Long wick candles
- Big lots on tape (ask) after a decline = indicates short covering