Practising does not always mean "working on". It’s important to give yourself time with the passions and skills in your life to just simply indulge in the activity. It's vital to allow yourself on occasion to indulge in pure enjoyment. This helps you remember why you do this thing in the first place, and can give you energy for further training later—if that's your desire.
If you've been working hard in your training it can be difficult to switch gears from training brain (a necessarily critical space) to enjoyment brain. Here are a few tips:
Focus on Feeling Instead of Outcome
You need to switch your judgemental brain off. Tell your training partner what your goal is so they can join you in it. Tell them you're not worrying about winning or surviving or "doing it right" and that you want to simply indulge in your body and its movement. Often all that's needed is to give yourself permission to "let go".
Play a sparring game like exchanging blows, mortal/immortal, or back-against-the-wall. Changing things up by giving yourself a particular objective that allows you to get away from the rigours of whole art training can be fun.
Do Slow Fencing
I'm a big advocate of slow fencing for training purposes, but it can also be a way to step away from your combat brain and simply step into the art instead of the competition.
Do Something Completely Different
If I feel really stuck in criticality I sometimes switch to something completely outside of my known realm. I change to postures that are entirely different than the ones I normally use, or work on a different weapon discipline. This can allow me to let go of expectations (assuming I have no skill in the new area) and enjoy the process of learning all over again.
This idea of switching mindsets is not limited to the sparring environment. Vary your objectives in class. It's completely wonderful to let go of the objective of "getting better" while being instructed and instead simply enjoy your body, the camaraderie of your peers, and the beautiful art we all share in.