After doing well in practice and back-testing, and then totally massacring an EA, I took the weekend off getting my head straight. Today there were trades that last week I could have convinced myself were acceptable but weren't in my plan area. Looking at the sticky note with the amount of money I have lost while being undisciplined made me look at my computer, shake my head, and go find something useful to do.
FOMO is a real thing, and it can come out when you least expect or even when you are prepared (I am assuming that when an EA gets to a PA I will have to deal with it on a different level).
But today I did well and looked at my past mistakes and realized where they came from, what they were preventing me from achieving, and how silly they were. Stay alert, stick to plan, get through the tough times!