Zum has decided that he wants to stop on the trail. He is not afraid or nervous. There is no obvious reason why he will suddenly stop. Kicking him or kissing at him makes him back up. Pulling one rein to the side results in Zum bending his neck to look at me without moving his body. Sometimes I can get him to move forward if I smack the end of the lead rope against my thigh. Waiting sometimes works as he will get bored and then want to move forward. Usually I have to get off him and walk him forward for a few yards and then get back on again.