Is it normal to be doing fewer reps the second session after beginning resistance training? Last time (the first time) I did my squats/pullups day I could do 4 good pullups on the first set before switching to the jump-up-and-slowly-lower-down sort. Today I could only do 2, and barely. I recall this being the case in earlier times starting up resistance training – I would be able to bust out a fair number of pullups the first time after not exercising in months (much to my surprise!) and then this number would decrease the next time I tried.
Your ability to recover and repair is a ‘system’ to be developed, in the same definition as your ability to project force and maintain speed. If it’s unconditioned, it will take time to bring it up to standard, and until it is built up it will inhibit your other faculties.
If you like cars, think of it with this analogy: you can put the biggest, most powerful supercharged engine in a car, but if you’ve still got the rusty ass stock exhaust pipe on there, your power output will be severely diminished.
You first want to ensure you’re getting adequate rest. If you’re already at your personal limit for sleep at night, throw a nap in there. Naps are fun.
Second, you want to make sure you’re feeding properly (this was likely the poster’s issue). Getting appropriate fuel and materials to the site so that you can build, repair and maintain is vital.
Third, be sure you’re getting proper active recovery. Walks may seem boring and superfluous, but minimal-impact movement is key to getting everything recovered. The body is designed to be in motion; you “rest” better by going for a leisurely walk around the neighborhood or park than you do laying on the couch watching TV.
After that, just do your best as the strength and recovery fills in. If you continue to struggle you might temporarily scale back your workouts to let yourself catch up (for example, jumping from completely sedentary to 6 workouts a week can be asking a bit much for most people).