I lost my teens years du to anxiety disorders, depression etc. How do I prevent this in my teen?

Anxiety. Make sure you seek professional help for your kids at soon as you notice any signs of depression or anxiety. There are no good data on whether "preventive" intervention would be beneficial.
Treatment. The sooner a person is able to recognize the symptoms of anxiety and depression and receive treatment, the more likely they are to find healthier ways of dealing with the symptoms. If you see symptoms of either one of these disorders in your teen, the best way to decrease symptoms is to talk to them about it and seek treatment from a competent licensed professional. These issues are treatable!