Should I skip the afternoon trading session?

Let me offer some ideas for you to consider. Try the ones that make sense to you.

If you do not have edge, after measuring, during a time of day, then you should seriously consider skipping that session.
If you do not have edge during a time a day (again after measuring), at a minimum, you ought to analyze what trades do work for you during this time period. And be more selective to stick to these trades.
I like the idea of limiting risk during a time period that is not as profitable for you. I noticed that you lost 5k in a trade during a weaker time period for you. Would it make more sense to set max loss limits on trades for the midday?
We work with traders who view the open, midday and close as separate trading businesses. They have a distinct PlayBook for each time period.
We work with traders who take scheduled breaks throughout the day to recharge and reset for a distinct time period. One large experienced trader, who I work with outside our firm, added scheduled breaks to his trading for lower stress and improved trading.
There are several traders on our desk who hit the gym midday. They use scripts, that they have built with firm technology to enter the best opportunities, if not on the desk.
Could you have made more than 7k on the open and lost less than 5k during the midday? Please make sure you are spending most of your time trying to make more from your best trades.
What does this have to do with discipline? Did you have a rule not to trade midday? If you have not even built these rules for your trading, then this is an issue of business planning.
Build a PlayBook. Trade your PlayBook. Get to the point where you can quickly determine whether you are taking trades in your PlayBook or trading outside of your PlayBook. Your PlayBook is your business. Stick to it, while slowly doing R&D daily to expand your PlayBook.
My partner, Steve Spencer, has always advocated for a give back rule. Once you are up significantly on the open, then set a rule for what percentage you can give back.