Why do you need a coach? I am not talking about a personal trainer here. I definitely believe in personal trainers, but I also think that soemone who has lofty physique goals should have a coach. The reasons are numerous.
Accoutability
Perhaps the most obvious reason to have a coach is accountability. Everyone does better when they have a coach to hold them accountable. The knowledge that someone will be asking questions and expecting to see positive results is generally enough to keep people on track.
Knowledge
A coach has knowledge that can help you reach your goals. It is important to remain open-minded and listen to what the coach has to say. Sometimes it seems counter-intuitive. Anyone who has gone through a preparation cycle for a bodybuilding show will know what I mean. Eating dry carbs the day before the show? What? But it works exactly as my coach described to me.
Intensity
Some people need someone present when they train in order to achieve maximum intensity. For me it is enough to know that my coach will be reviewing my training log. That causes me to get that last rep. I push myself harder when I am working with a coach. It is just my way of operating. I don't want to let anyojne down ever.
Creativity
A coach can bring some creativity to your training and nutrition plan. They will have you doing things that you never thought of. It will help you achieve your goals because you won't ever be bored. The challenge is fun because it is different.
Cheerleader
A coach will be your cheerleader. When you are down and not feeling it the coach will be there to help you through. I've had that experience many times. That kind of support is invaluable.