I ride once a week on a horse called Charlie, and he is lovely to ride. However, on the ground he is not so lovely. When I pick out his feet he is always trying to pull his foot away, and after about 10 seconds he slams his foot down. I'm not allowed to do his back legs because he tries to kick, so someone else does it. When I am untacking him, he wanders off when I take his bridle off (as in, motivated walk, not just a few steps). When I lead his too the field he drags me around and tries to eat the grass. He did not used to be like this when I first started riding him (about 4 months ago), and the last time he started to wander off when I was untacking him I got told off for letting him do it as I "have been riding long enough to know what do do". But I don't know what do do. Is this normal behavior and am I just being weak? what can I do to stop his acting this way?