This is very simple. Most western world thinks they are sick because of outside factors, environment, viruses, heredity, etc. But most important thing to know is the disease forms from eating the wrong foods. Of course we get viruses from outside and our own negative thoughts impact our well being, but food is number one. We eat too many junk, processed, Sugar laden foods. So first thing you can do is change your diet.
Abuse to your body for many years makes your liver and pancreas tired and loaded with toxins. In fact all cells in your body become toxic. But there is hope. Our bodies are very flexible. In order to restore the body you will need to cleanse your organs, it will take time. You do not become sick overnight and also do not become healthy overnight.
So start eating raw plant based diet (may be you can eat meat later on). Do a colon cleanse, kidney cleanse then liver flush. It may take more than one liver flush. Also if all cleanses don't change your health much then I would be on water only fast. Fasting with water only fir 30 days will cure most if your diseases.
My Depression went away in one flush. I am a born vegetarian, but ate a lot of processed junk and now I don't get sick very easily.