Recognising when your horse is trying and shaping their lessons accordingly is the key to success in training.
In pressure / release training, the ‘learning’ comes with the release. It is of the utmost importance that the trainer be able to recognise the slightest try offered by a horse and be realistic in their expectations given the stage the horse is at. There is nothing more frustrating or disheartening for any student than having their try ignored. Before you start applying pressure, have a plan. Make sure you know what it is you want your horse to achieve and tailor this to the stage the horse is at in their learning.
For instance, the first time you teach your horse to back up from the ground you would not expect them to be able to march backwards in a straight line for 10 steps. Instead you might expect him to take one step. In applying pressure for the back up for the first time your horse may respond by pushing into you, going left, right or even up. This isn’t them being bad, this is them just trying to find the correct reaction to get their rest and reward. If at some point they start to lean their weight backwards, you should release the pressure as they are ‘trying’ this direction.
This initial try is the foundation to the first step back and you can build from there. The next time you would maintain the pressure until the horse took a whole step. Then build it to two steps, three steps, or whatever the desired result might be, before they rest. It is a fine balance between building these steps and keeping the horse trying. You know when you have it right when the horse offers you more and more each time. You know the horse is really engaged in an exercise and their learning if you get to this stage.