Ultimately, you decide how you feel. The environment can greatly influence your decision, but in the end, you are the commander. Mental disorders can be fixed. Isn't evolution sufficient evidence to prove that things change over time? Adaptation is the key element. We've learned in our past through our own ideas to let ourselves be capsized because it's our safezone. He is not the only one with this theory. There are many others, including Miguel Ruiz with "The Four Agreements" just as one example, along with Robert Greene's "Mastery." Do not let yourself dissolve in a perpetual hell. There is a brilliance in all of us!
Free will does not exist. Some mental disorders cannot be fixed. Also, they may worsen over time. There are disorders that fit in the category of "learning to live with it". Evolution has nothing to do with it. You are just as a stranger in your own world as he is. My advice is to learn about the nature of mental disorders.