I have had a number of clients who recently retired and wanted to try flyfishing. A couple got the bug bad and are really getting after it. others only fish occasionally.
A school is a great place to start. I spend the first couple hours, and some times all day, trying to break bad habits of the self taught. Learn it right from the start and you won't hit a wall later as you progress.
The best advice I can give you is learn to use technique not strength. I tell all of my clients that fly fishing is a thinking mans game. Think before you start your cast and your casting will be more successful. Most people only focus on where they want the fly to go. Focus on where the fly is, where it needs to go and how it is going to get there. If you do this you will avoid the all too common collision between the fly, flyline and everything around it.
I know TMI but you have to start somewhere...
Oh yes, relax and enjoy!