This is seems so obvious but most people tend to neglect the mind when it comes to weight-loss and healthy eating. It doesn't matter what diet plan you are on, if you do not focus on dealing with your mind you are likely to fail. Ask yourself, why am I not as healthy as I should be? Are you emotional eating? Do you lack motivation? Are you depressed?. I also think that spirituality can help someone with their mindset, for example positive affirmations.
This is something that has been on my mind a lot recently in regards to my own issues.
I become so focused on calories, simple carbohydrates, sugar etc that I neglect another important part of the process.