I disagree - horses personalities can change overnight.
Take them out of their usual environment and they can become very unsettled acting like nutters because they want to see all that is new around them.
Trista says that she is not overconfident so, when the horse started to misbehave she probably worried or tensed up and the horse sensing this, acted worse until he was completely taking the mickey.
I agree Trista that you need someone to come in and help you ride him through these problems and would suggest that when he is not being obedient with his manners that you get very cross with him. Not to beat him up or anything like that but to get hold of his halter, give him a few hard jerks with the rope, make him back up and chase him away from you in a circle on the rope. Generally make him think that you are the devil himself then stop and continue as if nothing has happened.
Take command in no uncertain manner.