sounds like the main thing you need to do is learn to relax and concentrate at the same time, i think maybe you just need to tell your RI what you have wrote in this thread, you might be like me and just have a lack of self confidence when riding and faith in your horse!
the things you have mensioned there cant really be helped by just telling you how to do it correctly!
just a case of practice makes perfect, but unfortunately it doesnt happen over night!
any way im sure your lesson will be great and really help! im always complaining that im not doing stuff right, then people watching just laugh at me and say you were going lovely then stop being stupid!