A particularly valuable function of coaching is the ability to provide fresh perspectives on problems. As the Einstein quote suggests, attempting to solve problems with the same ways of thinking that created those problems can only lead to self-reinforcing and damaging cycles.
If you think about how coaching occurs in performance fields--from performing arts to chess to athletics--you will see that coaching is always hands-on and coaching is always real time. The hands-on, real time aspects of coaching enable the fresh inputs of a coach to become integrated into a process of learning and deliberate practice.
Can you imagine a basketball or football team where players were expected to keep journals about their performance and meet with a coach once a week to work on improvement? Of course, it would never work. Coaches work with performers daily, observing practice sessions and actual competition to offer concrete feedback and work on specific skills. This is why so many excellent coaches have performed in the areas where they now help others: it is difficult to give performance feedback if you don't understand the nuances of performance in that specific domain.
One of the great challenges in trading is bringing coaching to a hands-on, real time basis. A skating coach would never meet with a promising skater in an office and discuss, second-hand, what happened the week before on the ice. Real coaching takes place on the ice.
I predict the next breakthroughs in trading psychology will occur when coaches and traders are on the desk and not in the consulting office.
Further Reading: Mentorship, Coaching, and Why Traders Fail