Quote from lindq:
Not worth the hassle, unless you have a system that specifically calls for it.
My suggestion is to keep things simple and focus on just nailing the single position as best you can. That's challenge enough.
In my experience, concerning myself with adding to an existing position either on strength or weakness just complicates the trade, and often leads to entry errors and added trading costs that over time negate any extra gains.
I agree with this.