I know how it sounds. I know. But, as a riding instructor I can speak from the experience of having genuinely seen it work in every client of mine that has tried it.
As I've written about on many occasions, having an independent seat is vital for good riding. Common problem areas are tension in the hips/pelvis, stiffening of the back, and stiffness of the arms or shoulders. If you are stiff, tight, or restricted in any of these areas, it will almost certainly impact how you ride; your balance, the refined communication with your horse, and your horse's ability to carry you well.
One of my favourite (albeit newer) techniques to improve tension areas is to "breath into" that area. Some people find it really easy, and it comes quite naturally for them, for others it takes work. As a rider myself, the thing I struggle with the most is actaully remembering to do it!
It's easy to learn and practice. Try it now, it takes a maximum of a minute.
We'll start with toes, because I always find them the easiest and once you can do that reliably well, then focus on the "problem area".
Inhale. As you exhale, visualise the air going down into your toes. You'll know you are doing it right because you'll probably start to feel a "tingly" sensation.
The more tense and tight an area is, the longer it will take. If you are struggling to get it, it may also mean that you are tackling the wrong thing. Gripping with the knees and thighs, for example, almost always originates from tightness in the hips. Focus on breathing into the route cause of your tension, not the symptom.
I am a dressage trainer and general equestrian coach in Surrey, Sussex, and Berkshire. I teach dressage lessons, and hold a range of riding and equestrian clinics around the UK, and use my blog to share horse training tips, advice, and resources.