You don't have to be inspired to improve, but you do have to be organized and improvement-oriented. If you always wait until you are fired up with your concert face on, you will likely be doing more moping than practicing. Moments of awesome music-making are probably not going to happen every time you open the case. So get used to it, and plan on making improvements regardless of how you feel.
This should be good news. You can build your playing even on a bummer of a day. Feelings don't have to govern progress. Decide what issues need addressing and plan to cover them wisely and consistently. Now, rather than a checklist to complete, your daily goal is improvement and consistency. Your assignment is to get better as fast as possible. If you are not getting better at a noticeable pace, practicing is a waste of your time.
Let's pick at random three typical "issues" that you can work on no matter how good or bad you may be feeling. First, everyone must have a good DT. How about mastering an even double-tongue by next week! Why spend a whole year trying to remove it from your Nemesis List? Fix it now so it is even and clear, with your tongue front-and-center. Get your K to sound like your T. You don't need 20 teachers. Just do it. We have so much material for reference. There is no excuse for faulty tonguing. Lots of dumb players have mastered it, so it is doable.
Next, let's take on the Tubby-Unfocused-Dead-Sound problem. You're most likely dispersing your air stream rather than focusing it on a smaller target. Tighten corners, direct the air straight ahead, no blowing down, and no puffy cheeks. Buzz the mouthpiece at a mirror. Try to pin a $20 bill to the mirror with only your buzzed note! Next, create a nice fog on the mirror with as high a note as you can. Think more Lazar, less tuba. Whatever it takes, you must conquer the TUDS problem. Also, a less heroic, more conservative mouthpiece cup size could make a big difference.
Finally, there is the Universal Fatigue Disease. Make this as uncomplicated as possible. Stop playing before you observe symptoms! Don't go where the disease is rampant. Keep chops healthy. Don't make them work so hard. Develop endurance without getting sick. Build your strength zone instead of venturing into the danger zone every time you play. More brains, less macho. UFD can be avoided. See to it.
Don't feel like practicing? You're missing the point and the chance for progress!