There is perhaps one useful point to these early dark night if you have a school with floodlights and that is the shadows they cast. They can almost work like a mirror to give you a quick check that you are sitting upright and how your horse is working.
There are only certain areas of a school normally that will give a good shadow which are normally directly opposite the light source but take a look next time you ride as they may help you quite a bit.
Or you can take silly pictures of your horse looking like a camel, like I do?