In a previous tip, I said you are in every story you write. That’s true and knowing and using that fact can make your stories better.
Whenever you character gets into a difficult situation… and they always do because stories are about characters in difficult situations… and you are considering various ways for said character to deal with said difficult situation, think what you’d do if you were in their place.
You might not be a Navy Seal if that’s what your main character is, or have magical powers or whatever other special attributes you’ve given your character but I’m absolutely certain that you know how you’d take care of business if you were a Seal or did have extraordinary powers. And, knowing that, you know what your character should do. What you’d do if you were your character.
That action makes that character believable. Makes him or her real. Gives your writing honesty. And makes your story one readers will remember long after they’ve put the book down.