Is proper nutrition all that is necessary in order to be healthy forever?

No: Were it that simple! 'healthy forever' involves avoiding nasty things like drugs, excessive stress, exposure to toxins etc. Wearing a seatbelt is another important factor. Health is a multifactorial matter.

No: Proper sleep, lower exposure to toxins from the environment, the ability to handle life stressors. Nutrition is important but it is only one of many factors that involve in healthy, their is psychological health as well as nutritional health. There is also spiritual health and physical health. All are important and need to be addressed to have a well balanced life.