My mare for he longest time would not give me any speed. She would do a slow lope and that was all I could get out of her. There were 2 reasons for this; diet and respect. We had her on sweet feed for a long time, and for 2 years I never once saw her play wih the other horses. But, we switched her to safe performance and within a week I saw her teasing some of her pasture mates and she Also started giving me a lot more energy under saddle. The other thing was respect. She had an amazing lack of respect for me. And don't think just because your horse listens to you that they respect you, because human respect is way different than horse respect. If you find your horse pushing you, standing right beside Or on top of you a lot, they are nippy, they shove you, etc. your problem is probably a lack of respect. I would recommend watching a few episodes of downunder horsemanship. If you look it up on google it should tell you when and what channel it's on in your area. Neither of these may be the problem, just making a suggestion.