This image didn’t allow me to set up and use ideal settings. Had I done that, the person would have been gone by the time I was ready.
What I’m saying is that you shouldn’t be too focused on getting everything perfect. The Rule of Thirds is a helpful compositional guideline but it’s not the only way to do things. Capture the image you want even if that means breaking the Rule of Thirds, Golden Ratio, Rule of Odds or whatever other compositional guidelines you’ve learned about.
This requires practice. Neglecting everything you’ve learned can be confusing. But it’s a matter of knowing when to forget.
I’ve found that the best practice for this is to choose days or sessions where you restrict yourself to only one lens and leave the tripod behind. This gives you practice in how to react fast and correctly whenever you find yourself in a similar situation at another stage.