Sometime, life get in the way, we have to prioritize other things. What are your reasons for not trading on certain days?
I trade forex on the side so I’m not super strict when it comes to my trading schedule. 
But usually, when I’m not feeling great (physically, mentally) or when I have to work on other things for my other freelance activities. 
I don’t normally trade on Mondays or Fridays, as most FX pairs are redefining their postions, by the big banks. If my mindset is not focused on trading, or none of my selected FX pairs meet my trending strategy process I close my laptop and find other things to do.