think out loud
I would get annoyed when I would answer a 6-mark GCSE Maths question correctly, but only get 2 marks. All because I didn't show my working out.
"Well, my answer is correct." I would reply. "That's the main thing, right?"
Wrong. The purpose of showing your working isn't solely to get the marks. It helps you understand each step in the problem-solving process. It's a good habit to build, especially when problems become too hard to solve in your head.
It sounds like a flex to say you can do it all "in your head." But our brains are much better at processing information, not storing it. If we put our memory to the test, it often fails us. Little mistakes in values can give incorrect answers with most mathematics problems.
When you show your working, you let the page be a storage place for the thoughts your brain comes up with. This gives your brain more space to figure out the next step.
Showing your working starts with thinking out loud. Writing helps me do that, as well as audio journalling. As I'm getting older, I am prioritising reflection and pondering about problems and ideas through writing. It's made a positive difference in how I approach new situations.