They say it takes at least 300 reps to form a new habit and a whole lot more to replace old ones, yet I quite regularly see someone's golf swing fundamentally change within an hour.  As Nobody can learn something new that quickly, I can only conclude that they have been somewhat already there. 

Learning a golf swing can be an incredibly intimidating prospect. Still, it's much easier than staying the same, as a swing devoid of universal movement skills is a lot more work long term.

We each possess universal movement skills; they are a combination of pure instinct, like walking, or something learned early in life, like throwing a ball. The underlying control of said skills has been in development for your whole life; as such, a golf swing in which your universal movement skills are represented is as close to a person's ‘natural’ swing as you will get. 

Kids learn quickly, free from the shadow of past failures and unaware of consequences; they will progress in golf largely irrespective of coaching; most of my time with that age group, my time is spent convincing the parents that perfection will not be the result of rigid instructions. I'm particularly intrigued by the challenge of coaching adults and beginners. Not only does it make for better conversation, but they can better appreciate the impact of my intervention.

When it comes to making changes for adult golfers, you might think that the greatest limitation is of a physical nature; I have found this not to be the case, as it's easy for a decent coach to build a swing around physical limitations. The true hurdle is that the average adult hasn't learned a new skill in a long time and prefers to recruit a slight variation of learned skills for new tasks. e.g. using their cricket technique for golf. Their experience with these learned skills is more surface level as the foundation was set long ago.

Why is it so hard to change? I suspect there is a sense that their current golf swing may be compromised by new information. This sense stems from a misconception of what exactly their golf swing is. Let me explain; A golf swing is not a collection of thoughts, feelings, or intentions; such things cannot run a compound skill all on their own any more than I can fly a plane. 

Someone's true golf swing is what objectively happens when faced with intensity or pressure. The aforementioned thoughts and feelings serve as a mental anchor and are often integrated into a pre-shot routine, leaving little room for anything other than panic. 

A good golf coach can help you integrate universal movement skills into your golf swing. In the interim, by practising the art of not giving a shit where the ball goes and disregarding the notion that the next shot needs to be straighter than the last. This process opens a void for your most universal movement skills to fill. You should expect a consistent shot pattern to emerge; it probably won't be that baby draw you have been chasing, but it's a great start and will present the original problem.