Here is a training thought for the day: break your ride up into useful sections.
1. Free walk. Purpose: to get blood flowing to all the muscles and limbs. Make sure this is on a long rein, unless you absolutely cannot trust your horse. Make sure this is energetic enough to flow the blood appropriately, but do not rush the tempo. Fast tempo will reduce your swing, which reduces your future impulsion and suppleness. A good walk feels like gliding. If your horse is stiff legged and not gliding, relax your aids, and try spirals. Enthusiastically praise your horse while he is working. This should be about 5 -10 minutes depending on if your horse has been stalled or pastured, etc.
2. Warm up. Purpose: to supple the horse in walk, trot and canter. Frequently, I see riders make the mistake of keeping this part of their ride exclusively a trot. Make sure you supple all three gaits. The suppling exercises that you choose should be appropriate for the level you are riding. Look to your tests for ideas. Make sure your horse has enough bounce in his step at trot and canter. Bounce can be rider created if your horse doesn't have much on his own. Make sure you do many transitions. This warm up phase should take around 10 minutes, on average. It may include a short walk break if your horse is out of shape. In the ten minutes you should have done 20-30 transitions. The avereage person does maybe 4. However, if you are on a very hot horse that won't hold a nice tempo, then a long steady trot set may be appropriate. If your horse is inactive in the hind legs, do a lot of trot canter transitions.
3. The Meat of the ride. Purpose: to create collection, which is also the purpose of dressage. Collection is about rebalancing the horse. Really focus on the hindlegs, the quality of their reach forward, activity level, pushing power and regularity. Even training level horses have this as their purpose of the ride. However, the expectations are lower. Praise all the good stuff during the good stuff. Don't wait till walk breaks to praise. Sometimes you will have to take a walk break or two during the meat of the ride.
4. The cool down. Usually 5 minutes or so. It should be done in the horses' two most calm gaits, usually trot and walk. Be sure to stretch the topline long and low with changes of rein in the stretch. More free walk to remove lactic build up. And praise!
5. Older, stiffer, special needs horses: add a cool down in the barn with in hand stretching of the limbs while the horse is warm.