It's something you cannot force - the horse needs to be able to carry himself without leaning on your hands. If your horse is young, he may be unbalanced and be looking to you for help. If he is older, he may just be a bit green and need further schooling. If your horse is an 'older' horse, there may be problems with his muscles, teeth etc - or if you haven't had him long again he may not have had much schooling.
As cvb says, more info please!