Happy to take good advice

First off, I have a great trainer, who also happens to be my 19 year old daughter. She has taught me everything I know about riding, and us doing this together has been a blast. But.........I am just not getting my body to do what I want it to do when riding English. My legs keep sliding forward, and I hit the saddle way too hard and bounce.
So last night I went to the barn to ride, without my daughter. Which is a rather new thing, but I feel as though I can do that now, I can go ride even when she can't come and that is pretty cool. Well, as long as there are people around, in case of an accident (we live by the rule: NEVER ride alone!). My son came with me last night, even though he really does not like horses or the barn, but loves his momma.
Pippi was in the field, but came when I whistled and was quite ready to go back in after a full day outside. We use a special whistle when we call her from the field, to varying degrees of success, but it is super fun when she looks up from grazing and comes trotting over happy to see us.
After brushing her and tacking up, I was ready to go. Pippi is very kind, and especially so to me. She knows I am a novice and takes it easy on me. We walked for a long time, and then I asked for the trot. As usual it was touch and go, I know my diagonals, but my seat just is not right. Pippi knows it to, and slows to a walk to let me know that she does not appreciate the heavy bouncing on her back. She is a great teacher that horse.
Now, I know what I want, I just can't get my body to do it. Recently they got some new help at the barn, a young woman named Jamie, who I immediately liked. She seems to be tough, no nonsense, and quite friendly. Spotting her, I took my advice ( I always tell kids to ask for help), and asked her to check my form. She came into the indoor arena, and corrected my seat. Pulled my legs back, asked me to sit on my butt, and then slide forward rocking my hips, and straighten my back. That's it! I have been trying to create a curve in my lower back that is not necessary, it is all in the hip joint rotation!
Off we went, and Pippi stayed in the trot for as long as I wanted her to. We did figure eights, we hopped over some poles, we were DOING IT!!! Trot trot trot. I was rising and falling smoothly and without bounce, my legs stayed put, my back did not hurt because I was no longer struggling to arch it, and I was ecstatic!

It is always a good idea to ask someone else to explain something to you if you are not getting it. They may give you a whole new explanation that finally hits home, the key that finally unlocks your issues. Can't wait to practice some more.
Just wanted to show off my Pippi again: