If you were to look at the state of the world today, no one would blame you for being pessimistic. The problems are real, don't get me wrong, but you don't need to feel defeated; that is a state of mind. Whenever you hear the word "can't," swap it out for the word "won't."
Let's look at the difference in action:
I can't learn to code.
I won't learn to code.
I can't be an artist.
I won't be an artist.
We can't fix the climate.
We won't fix the climate.
"Can't" is impossible, "won't" is a choice. That means that most problems we face, either in our day-to-day or significant societal issues, can be fixed – you need to choose it. Reframing what is possible has left me as optimistic as ever.