In a world of conflicting advice from all sorts of health and fitness professionals, it’s easy to lose sight of the most important principles of health. I find it refreshing and a breath of fresh air to return to the wisdom of some of the greatest minds of all time, and simply get back to the basics.

With that in mind, here are eight quotes that are centuries old, yet still shed light on what makes for optimal health.

1. “Pleasure in the job puts perfection in the work.” – Aristotle

Do you often wonder why it’s so hard to keep to your diet and fitness goals? We often think in terms of seeking enjoyment or pleasure for its own sake, but if an activity is productive, Aristotle teaches us that it can also be the key to its perfection and optimal success.

The same applies to diet and fitness. If you resent your diet plan or dread your exercise routine, it’s only a matter of time before you throw in the towel. Make sure your exercise workouts are varied and fun. Add some of your favorite foods in moderation to your meals and avoid extreme diets. Then not only will you take pleasure in the journey, but you’ll also succeed in your health and fitness goals.

2. “Without exercise, a good diet alone is not sufficient and eventually medical treatment will be needed.” – Hippocrates

In a world where “skinny” is the ultimate goal, we often associate it with idyllic health. But looking skinny, even if you’re eating a well-balanced diet, is simply not sufficient for ideal health.

Hippocrates, the father of Western medicine, wrote more than 2,000 years ago about the many health benefits of exercise and the illnesses that result from a sedentary lifestyle. Simply put, without exercise, you’ll eventually require the expertise of a doctor.

3. “Walking is man’s best medicine.” – Hippocrates

With so many new fitness programs out there, it is easy to feel overwhelmed, which often leads to skipping exercise completely! One of the most effective exercises is a simple walk outside. If you cant make it to the gym or just aren’t in the mood to work out, don’t skip your daily exercise. Take a walk around the block for 10 to 20 minutes, and you’ll still gain the many health benefits of cardio exercise.

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4. “If we could give every individual the right amount of nourishment and exercise, not too little and not too much, we would have found the safest way to health.” – Hippocrates

Even after all the recent achievements in science and medicine, exercise and diet are still the most effective health solutions. The key is to find the right balance. Don’t overexercise or overeat, even the best foods. Don’t under-eat or do too little exercise. Moderation is fundamental for optimal health and prevention of illness.

5. “Don’t explain your philosophy. Embody it.” – Epictetus

We often talk about our fitness and diet opinions with enthusiasm, yet fail to actually implement them. We have grandiose plans and complex resolutions. But how real are our beliefs if we don’t live them? Turn your theories into action, starting today!

6. “One should eat to live, not live to eat.” – Benjamin Franklin

We all have our favorite foods and ‘treats’. There is nothing wrong with making exceptions once in a while. The problem is when exceptions become the rule. The body requires food for its sustenance and its vitality. How many of us really view food this way? Think about it. The food you eat does not simply vanish. Every cell in our body is affected. Choose foods that will improve your quality of life and health.

7. “God has entrusted me with myself.” – Epictetus

If you don’t take your personal success into your own hands, no one will do it for you. We may not be in control of every external influence or experience but we do have free choice and control of what we do and think. Excuses and placing blame on others or situations will simply stall any progress. Start with small practical changes. Ultimately, your success is dependent on you.

8. “A peaceful heart leads to a healthy body.” – Proverbs 14:30

Both ancient writings and current scientific research show that stress affects our emotional well-being and physical health. Exercise has been shown to reduce stress significantly. Find ways to distress everyday and make the most of your life and well-being.

This article first appeared in mindbodygreen.com and is written by David Zulberg. David  is author of The 5 Skinny Habits: How Ancient Wisdom Can Help You Lose Weight and Change Your Life Forever (Rodale, October 2014).