Just keep up what you are doing and lope some large slow circles. Small circles are very hard on horse. Eventually try trotting up some hills and maybe some sand. After I have one in pretty good shape and heart rate and breathing slower, I start breezing a short distance then walking then breeze some more, etc. Just like you would build yourself up to more strenuous activity, take your time with your horse. I firmly believe that the better condition your horse is in, the less chance for injuries you will have. Hope this helps a little but sounds like you are already on the right track!