Unfortunately this is the season not for blazing practice frenzy, but a sudden shortage of fuel for the fire, commonly called burnout. Nearly as contageous as the flu, it approaches stealthily taking its unwilling prisoners. The usual symptoms are unproductive practice sessions, fatigue, and motivation turned cold. If only the remedy were waiting it out with a couple of aspirin!
Some suggestions based on trial and lots of error: First, the good news is that no one is immune. Struggling with progress, or even trying to maintain your ground, is part of the business. It is universal. Keeping motivated is perhaps the most difficult long range assignment. It separates the O.K from the greats. Vince Cichowicz confessed that only 10% of the time did he feel like everything in his playing was going the way he wanted. The rest was working to conceal and deal with the 90%.
Learning how to handle challenging obstacles is one of the marks of great musicians. So when we are down-in-the-dumps, we can take heart. Here's our chance. This is how it's going to be. We must get used to it. Gather your own collection of inspirational tips, and begin using tomorrow to find your voice. How well can you play when your heart isn't in it? Remember Pagliacci?
When inspiration runs out, never mind concerto run-throughs. Use the day to polish needed details. For example, drill your trills. They should be clean, in rhythm, and appropriately graceful.
Another pesky necessity is first notes. As long as you're bored you might as well improve something. Rehearse tons of entrances, playing only the first notes. Get each entrance perfect. You know you'll be needing them.
How about taking a few short phrases from your solo, excerpt, or etude repertoire, and playing them at a snail's pace, perfectly in tune. Be sure to listen to your last notes as well. They rarely get enough attention. You must finish the phrase as nicely as you began it. Know your entrances and exits.
Then you could have a quality-only day. (duh!) Allow only slowly played top quality notes out of the bell. Pinched, inhaling notes will not be rewarded. Only money notes permitted! This should shorten your sessions considerably! It will also save you from wasting your time and your lips.
There are countless items to work on that don't require artistic inspiration. How about fast scales, chromatics, arpeggios, or high and slow speed multiple tonguing. Fermata with dim. is another one. You can come up with your own list of needed refining.
Chances are that you'll find your uninspired mood being replaced with confidence. Disciplined basics give you the tools to be expressive and in control. Then life in the practice room and on the stage can be fun. No longer hamstrung by your deficiencies, you will be free to execute the demands of the music. Burnout begins when we ignore control of basics. Most of our work must be done whether inspired or not. So just do it, and don't whine about burnout. It is fixable!