Drafts and draft crosses are commonly used as lesson horses because they're solid, sane, and safe and generally their gaits are easy to ride. A safe, gentle ride is more important than a soft mouth for a rider just learning or addressing bad habits. That's why they used her. So now that you've graduated to another mount, your seat is better and you can concentrate on soft, giving hands. Another step along the line. Enjoy and don't lament what has happened in the past-- take what you learned and move forward. Now that you know what sluggish and dull feels like, you know what NOT to do with your future horses.