Why my mind was always tension.

Many possibilities: I have no way of knowing without a detailed consultation. Tension can be related to your genetics &/or environment. You could be deficient in essential vitamins, minerals, Amino Acids or essential oils. You might need counseling. Meditation, exercise, herbal & homeopathic medicines might help. A forum like this can't solve complex chronic problems-please see a good doctor with a holistic approach!