For me trading a butterfly is about managing risk and not anticipating the market. My biggest problem in this business came from anticipation. I might do smaller trade directional trade when I have a strong opinion and I have to scratch the itch. Often I will do it in an other underlying so not to confuse one trade style with the other.

As for profit goal. Normally that should have been part of your trading plan (made before you enter). For 20% is beautiful level to pull at least part of the trade. In a normal market if the trade is still in good condition. I might scale out in steps. Half around 20% and the rest around 25% and 30%. But in this market I am happy with what I can get quickly and don't push it too hard.

Ernst