The body is a chemical factory.  Every thought created in the mind has the potential to stir up new ingredients that add to the mix.  You are the scientist, creating and mixing and experimenting every time you have a thought … or not.  With no thoughts comes peace, for you are no longer a slave to the ups and downs, the highs and lows that hormonal/chemical changes cause.  Practice presence.  Practice no-thought so that you know how to get to “ground zero” – your innate state of peace.  From there, you will learn to consciously control your experiences of this world and beyond, but for now, start with the basics:  focus and presence.