Thought is life. What you think, that you are. Your thoughts create your environment. Your thoughts constitute your world. Every thought or emotion or word produces a strong vibration in every cell of the body and leaves a strong impression there.
If you entertain healthy thoughts, you can keep good health. If you hold on to sickly thoughts in the mind, thoughts of diseased tissues, weak nerves, improper functioning of organs, you can never expect good health, Beauty and harmony. If there is depression in the mind, the body also cannot function properly. If the mind is healthy, the body will be healthy.
Remember that the body is a product of the mind and is under the control of the mind. If you hold on to vigorous thoughts, your body, too, will be vigorous. Thoughts of love, peace, contentment, purity, perfection and divinity will make you, and also others around you, perfect and divine.
– Swami Sivananda