Anytime you are shooting line, it has to be part of your visual assessment routine to note line wrapped around the butt section of your rod behind the reel. This is particularly important with a two hander. The angler will most probably maintain a loop of line several feet long, which facilitates unwrapping the line from the rear of the rod, if it has made its way to the wrong side of the handle.
For a single handed rod for trout fishing, the loop is not usually maintained, so once the line is shot up the guides, it is important to look down and make sure the line is not wrapped around the butt. The line will be under tension. The problem here is the line will be under extreme tension/friction if counter wrapped around the butt. The fish/line will not be able to pull directly upon the reel spool/drag system. The tension of a large fish (should you be so lucky) on the tippet will make it difficult to unwrap the fly line to its correct alignment.