100%
Fundementally my swing has only changed a small bit over the years.... But my mental game is what's brought me down from 11/12 to 5/6 handicap over last 3 or 4 years.
Last week - cruising along +1 through 7 holes - birdied 8 to be level.... Triple bogied 9 out of nowhere.....
Years back - I would be gone at this point - mentally broken, angry, annoyed etc - I walked from 9th green to 10th tee.... 100 yards maybe... In that time, the score on the 9th is gone, new 9 holes, start again, one shot at a time....
Nice back 9 - +3 I think for next 9 holes. Shot 77 with a triple on my card.
I've learned very very well to improve on my mental game, enjoy the pressure of the game, tough shots etc.
Great book - highly recommended to read.
Be a Player: A Breakthrough Approach to Playing Better ON the Golf Course
Simple stuff - just very very good to work on the mental game as much as the physical side as well.