Horse slow to appreciate 1N?
There are two possible reasons a horse might find it difficult to enjoy 1N. One is physiological – their physiology is stuck in an equilibrium so the body resists change that might temporarily destabilise it - even though it's for the better.
The second is that some horses for various reasons find it difficult to relax. This may be exacerbated if the horse feels the need to look after others and is therefore worried about letting go and going “off duty”.
In the first case the 1N can be done super gently (Soft Start 1N) to make the changes to the physiology small and manageable.
In both cases the Respond and Reward, Control of Movement exercises are simple to do and can be surprisingly effective in letting the horse feel it's ok to let go and relax. They involve asking the horse for a simple specific movement using body language or gentle pressure on the lead rope and releasing the instant the horse responds, then following with a rest. Calmly controlling movement in this way persuades the horse that the handler is willing and able to take responsibility, so that the horse can chill or even sleep if they wish.
Control of movement exercises can be done using positive reinforcement if you prefer; so long as your horse is completely relaxed with food rewards, and the rewards are natural forage food that will not stimulate an increase in breathing.
Many horses immediately enjoy 1N but for horses that find relaxation difficult, gaining relaxation with Control of Movement exercises before starting 1N and if the horse fidgets during 1N is usually helpful for the first few sessions.
More on Soft Start 1N and Control of Movement exercises under 'Horse not getting it? on the How to do it page'