Here's a free swing thought that has nothing to do with mechanics: after a bad shot, take one slow breath before you do anything else. Not before you hit the next one — right after the bad one.

Most double bogeys aren't caused by one bad shot. They're caused by the rushed, frustrated shot that follows it. A three-second pause breaks that chain before it starts.

It costs nothing, it doesn't require a lesson, and it works on the very next hole.