He's not spoiled or soured, he is being disrespectful towards you. Not listening, not focusing, your just not as interesting as the other horses.
Taking him away from other horses completely is a bad idea. Its actually terrible to do. Horses are herd animals and most will not feel safe without the security of a 'herd'. They can also become depressed/ill from ulcers/stress while alone.
My advice is to find a trainer to work with you with him. He needs a firm hand you have have to make him realize that when he leaves, he will be coming back so it's not a big deal to go for a trail ride alone.
Take him out and walk away from the pasture. When he throws a hissy fit, keep coming to a certain point, and then turn around and head back. Repeatedly doing this will make him easier to handle and more comfortable away from the 'security' of his herd. When he starts to jig towards home as most horses will do, you turn in circles, back him or head back the opposite way so he's not walking all over you or rushing to get back.
I'd carry a dressage/lunge whip too if I were you. When he resists, you whop him in the butt and make him go. You asked him to do something...and he needs to do it. Having the whip as a reinforcement will really be helpful. Just carrying it will mean that you mean business.
Patience will be a virtue. Posted via Mobile Device