An effort to reverse-engineer Holmes’s methodology into actionable insights that help develop “habits of thought that will allow you to engage mindfully with yourself and your world as a matter of course
You Are Not So Smart: A Field Guide to the Brain’s Guile
This is another great book by David Eagleman. Incognito: The secret lives of the brain. David Eagleman uncovers wonders of our subconscious at work. One of my favorite section is on Ulysses Contract, Monogamous prairie voles and team of rivals.
After spending some time with Sagan, you may find Kant's argument against only thinking analytically rather refreshing. Your feelings and intuitions do matter (and in your 20s, you have a lot of them). He's a fan of a metaphysical understanding of the world and has some pretty good points to back it up.
How the Difference Between Your Experiencing Self and Your Remembering Self Shapes Your Happiness