That is due to cortisol and adrenaline
When I give a seminar I always say that at the end of each day I look like I gained 10lbs of fat and lost 10lbs of muscle… it’s so bad that I have to shower in the dark afterwards to avoid catching a glimpse of myself in the mirror!
Cortisol and adrenaline both decrease muscle glycogen stores, making you look flat and small, especially if it is a prolonged increase in cortisol levels.
Cortisol also increases water retention by increasing aldosterone and vasopressin levels.
To me, when you look significantly worse after the workout it means that you produced too much cortisol (either during the session itself, or the session just topped off a high cortisol release from the rest of the day) and this is definitely gonna have a negative impact on your gains (could even lead to regression).
Not being capable of getting a pump in the gym would either indicate lack of intramuscular glycogen or that water shifted more the extracellular component (so less intracellular); likely increasing subcutaneous water retention. This could also be a cortisol issue but could be related to carbs intake and electrolyte balance.
I believe that sometimes training WILL indeed worsen/hurt your progress. For example I used to train when I gave a seminar because I felt flat and needed to do some lifting because mentally it felts like I was losing muscle (I knew I wasn’t but the brain is powerful). I stopped that because I realized it did more harm than good. Training when your cortisol is already sky high is not a good idea and will greatly diminish the positive impact of the session, it could even lead to negative changes.
I’m easily addicted to training and I used to train 6-7 days a week no matter what. Even if I travels to the other end of the world I would force myself to train even if I was in a plane for 15-20 hours, didn’t eat much and felt jet lagged. I stopped doing that and I gained muscle and strength much faster. In the last 3 months there were weeks where I only trained 3x a week because of seminars and lots of traveling. But in that period I was able to go up from 220 to 233 and still had abs. Felt much better, much fresher. Sure I hate the days I don’t train. But now I simply use that frustration to get a better workout the next time I’m in the gym.
When I’m at home and don’t have any seminar (I had a week off last week) I will train 6-7 days a week, but when I’m in a high stress situation I don’t have a problem going down to 3-4. What I do is have 4 planned hard workouts that I can get in 95% of the time every week. If I can make it to the gym more often (less stress) the extra 2-3 sessions are much lower stress… isolation work, focusing on fixing weak links, no neurologically demanding exercises, higher reps, no longer than 40 minutes.
As for why is your performance just as good if not better when in that state; my theory is that you have less intramuscular pressure/friction which facilitate concentric muscle action/muscle fiber sliding.