be living proof of (something)
To serve as an example for why a particular statement or concept is true. As a former slacker, I know that you can turn your life around if you work hard enough—I'm living proof of that.
be ˌliving ˈproof of something
show something is true simply by being alive or existing: He plays tennis and golf. He’s living proof that a heart attack doesn’t mean the end of an active life.