The hardest thing to communicate to a golfer is the importance of changing their world view from outcome to process thinking because they have been conditioned from birth by society to judge their success from their results.
It takes a leap of faith to trust that perfecting the process, which includes staying in the present and not thinking, will produce the results one is striving to achieve. It's like trying to explain the 'sound of one hand clapping'.
Would you like to increase your concentration or keep from losing your focus during a round of golf? Would you like to play without fear or being nervous? Would you like to eliminate mental mistakes or mental collapses when you have the lead? Of course you would. By training your mind to play in the present, you greatly increase your ability to do so.
Playing in the present is exactly what it is - the present. You are in the present when you are without any thoughts or concerns about the past or future. Nothing else exists except the present and the truth of your circumstances. Your past brought you into the present and how well you do in the present will create your future. Any thoughts about the past or future take you out of the present and affect your ability to perform to your full potential in the moment, which is all you have.
Explaining the present is the easy part. The hard part is to fully REALISE that the present is the only thing that matters because it is the only thing that exists. Everything else is just a fairy tale that exists in your imagination or desires.
Golfers with a strong mental game realise that the present is all that they can control. They have learned to play in the present without concern about the past or future outcomes. They realise the power of just being in the moment with the full intention and expectation to accomplish their desires without attachment to the results. When they are at their best, they play on instinct and trust their subconscious or 'it' to make it happen for them.
Learning to play in the present on instinct requires time and effort. That is why experience is such a priceless commodity. Because when all else fails, the truth emerges from one's experiences if you are honest with yourself. By training your mind to play in the present, you can shorten the time required to experience the power of being free to play on instinct and in the zone. Unfortunately, many golfers never learn to stop dwelling on their past and future outcomes.
The trick to being in the present is to allow yourself to learn from the feedback each shot provides without your ego being involved in the outcome. By being honest about your present mechanical, strategic, physical and mental limitations, you will increase your awareness of what you can do to improve your present abilities. Then, it becomes a question of how strong your desire is to make the necessary changes or adjustments to improve.
If you don't have the desire or time to do the work to improve, that's OK. Just make sure that you play in the present without thinking or concern about the outcome so you can get the most mileage from your present limitations. If you do, you will shoot lower scores.