If you are already pretty proficient in coding, I would take a break from it and instead learn something different.

  - Sport (Snowboarding/Skiing/Swimming, Climbing etc lessons)

  - Reading books (History, Biographies, etc)

  - Visit a new town (doesn't have to be too far) and hangout with complete strangers and learn their stories.

Or purely on the STEM side you could refresh yourself on probability, statistics, linear algebra and get a deeper grasp on machine learning/data science.