Difficult To Catch
If every time a horse is caught they experience pleasant things, they will be easy to catch.
But, if every time a horse is caught they experience pain, they will not be easy to catch.
A very typical cause of pain, that the horse owner is frequently unaware of, is the pain they experience from a badly fitting saddle.
If your horse is difficult to catch and you know there's no other reason for him to want to stay out, use The Perfect Fit Saddle Fitting Kit to check if the saddle fits. If it doesn't fit, be sure you get one that does and, using the kit, check its fit at least every month, or more often if there are changes to your horse's diet or exercise.
Don't be surprised if he doesn't immediately become easy to catch. The memory of the pain will stay with him for some time, you will have to coax him into enjoying being caught and ridden so that you can remove the unpleasant memory from his mind.
When you are certain that the saddle fits well, if your horse is still difficult to catch, it could be that your horse remembers the pain that he was in previously, or, he is still in pain from the damage done by that saddle. If this is the case, you must have his back checked by an equine physiotherapist, chiropractor or osteopath. In fact, if a horse exhibits any unpleasant behaviour, the first thing to do is have him checked out by one of these professionals.
Sometimes it can take a while for a horse to trust that the saddle isn't hurting him, so be patient with him if he takes a while to become relaxed. Sometimes the upset that the pain causes him can create an unbalance of the healthy gut flora. This, in itself, is enough to cause your horse to be tense and exhibit undesirable behaviour. This unbalance can last a long time, so it is always worth giving a supplement of probiotics to a difficult horse.