Hang out with positive people.
Take a look at the people closest to you. Are they positive or negative people? Chances are if they are negative this attitude will reflect on you and your attitude. Try to limit your time with any negativity as this will only make you feel bad about yourself. You will focus on the things that you do not like about yourself.
Your body is linked to your mind. Many of the diseases of this era are psychosomatic. Stress and anxiety take their toll on our physical health. Meditation is a mental exercise which, among other things, allows you to detach yourself from the worries of life. Learn a simple technique and do it regularly.