Not to pile on here, but the others above have hit the nail on the head. Leave the expo alone for now (actually, leave all the advanced functions of a computer radio alone). As was said above, it's a crutch. If you use expo to "soften" up the throws of the plane then you will never learn to fly the plane properly. You will learn bad habits that will follow you to every plane you try to fly in this hobby, and in fact can make it almost impossible to fly some of the more advanced planes out there. About the only way to learn to not over-control is lots and lots of practice. This would be a great place for a simulator. I use this all the time for my students that have problems such as this. It allows them to get lots of practice in a short amount of time. If you don't have a simulator consider buying one, or at the very least see if you can borrow one.

Hope this helps

Ken