Mental exercises and learning

Mindfulness
I do certain exercises that seems to improve cognitive power. Mindfulness appears to cause gray matter neurogenesis in the hippocampus, see this article for more information: https://news.harvard.edu/gazette/story/2011/01/eight-weeks-to-a-better-brain/ — Eight weeks to a better brain

Wakeful resting
Another thing I do is so-called ‘wakeful resting’, placing yourself in a sensory-deprived environment and simply ‘doing nothing’, or at least, your conscious mind / focused mode is doing nothing, a lot is still running in the background, namely your subconsciousness or diffuse mode. This exercise appears to be so powerful that it increases retention with a whopping 40% after a week. These things really start to make sense when you read this article and book:

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0109542 — Boosting Long-Term Memory via Wakeful Rest: Intentional Rehearsal Is Not Necessary, Consolidation Is Sufficient

A Mind for Numbers: How to Excel at Math and Science (Even If You Flunked Algebra) by Barbara Oakley