According to Learn Like a Pro — a book for learners seeking advice from cognitive psychology and neuroscience:

“Exercise helps form a substance called BDNF [Brain Derived Neurotrophic Factor] in the brain. When you ‘sprinkle’ BDNF on a neuron … dendritic spines emerge. BDNF is like a fertilizer for [your brain]!”

[From Learn Like a Pro — Science-Based Tools to Become Better at Anything, by Dr. Barbara Oakley and Olav Schewe]

Be sure the “X” or “Exercise Factor” is part of your daily routine?