Crossover symmetry and some extra time on the bike, rower, or ski erg are highly encouraged. If you have any specific exercises you want to practice (double-unders, toes to bar, pull-ups) this is a perfect time to do some technique work before you’re dead tired.
Mobility work is great for problem areas but remember that rolling on a foam roller or lacrosse ball or banded mobilizations should be paired with a full range of motion movement to lock in the new position. Most of the new range of motion you get is neurological change and is short lived. If you don’t take advantage (for example doing a set of air squats after mobilizing the hips or ankles) of those positions, chances are they will disappear and your mobility work was wasted.
After you put away your equipment and clean up your space, if you have time, cooling down is very important. Spend 5-10 minutes on the assault bike or rower, or take a cool down jog or even a walk around the building to get your heart rate back down and help clear some of the lactate buildup from your workout. If you crush yourself at the gym, hop in your car and go straight to sitting at a desk all day, you are leaving gains on the table. Cool down properly after every workout.
Making sure you are properly fueled for your workout can make a huge difference in your training. A good general guideline is to eat the majority of your carbohydrates for the day during the 2-3 hours before your workout and the 2-3 hours after and keep fat intake low during that time. Fat slows the digestive processes and we don’t want that around our workouts. So some sort of lean protein source and healthy carbs (rice, oatmeal, sweet potatoes, etc) before your workout and after your workout another lean protein source (whey protein and water is a great choice) and a higher glycemic index carb (Gatorade or dextrose are great liquid sources) is your best bet.