Generally, optimists live longer. You might quickly come up with an exception to that rule. But in a 2020 longevity research, optimists or people who expect “that good things will happen, believing that the future will be favorable because they can control important outcomes” not only live more years but enjoy healthier years.
I resonate with this notion that people can set goals and control important aspects of their own future. You see, optimism is highly related to having a sense of agency and purpose. Purpose has already been shown in many studies to be a prime factor in elders’ happiness as they age. It also lowers the risk of premature death, promotes healthy behaviors and friendships, and staves off loneliness.
So, if you feel unhealthy or alone, what can you do?
First of all, it's important to understand and embrace the truth that you don't have to be this way. Unless you are dealing with deep, irrational and/or psychological issues that need to be treated by a therapist, your thinking is just that: merely your thinking. Unlike the weather or your neighbor's mood, you can change your thinking. This is not just a nice sentiment bandied about by New Age hawkers; Alice and I truly believe that if you "change your thinking, you change your life!"
As you believe in the possibility of your own soul, believe it is God. As you believe in God, believe in yourself. The more you believe in yourself, the greater becomes your love for others (of any stripe) and your optimism in a better world, co-created by your actions, is happening before you.
Do this and you will die in peace, joy and great hope that you are leaving a better world than the one into which you were born.