Originally Posted by txnative
My horse used to be awful about backing up when I tried to mount. To solve it, I got in front of him and backed him up a LOT. Then we'd go back to the mounting block. If he moved again he got another big back up session. Now he stands perfectly still for me.
I was going to suggest something similar...
Your horse needs to equate the mounting block with standing still. Work away from the mounting block, and when it's time to rest, let the horse rest next to the mounting block.
Practice walking up and down the mounting block a few times (be prepared to jump off) as though you were actually going to mount. If the horse takes a step, IMMEDIATELY back him up in a circle. Keep him moving until he is next to the mounting block again.
It shouldn't take him long to figure out that standing quietly at the mounting block is the easiest thing to do.