There might be a limit or a parameter to how much you can change or to how much good you can do. You might not be able to save everyone, but that doesn’t mean that there’s no reason to try.
It’s still important to have that broad vision of saving everyone and changing the entire world for the better. This vision is what helps us make a difference, our wide eyes are what allow us to be open to opportunities that help us get closer to our vision. Without the vision our mind is closed to opportunities. But if we don’t narrow our focus we won’t even be able to try, out of fear of failure or a sense of hopelessness in the task as it may seem too large to even attempt it.
Narrow your focus on the people you can help and on the things you can change, put all your heart into it, and that way you can change the world, one person at a time, one day at a time. Start with yourself, start improving, challenge yourself to be better at a level where your current abilities are slightly lower than your challenge, allowing you to stretch enough to grow but not brake. Sometimes you will fail though, but learn from the failures so you can improve, thats what failure is for; for us to learn and to improve.