if Naval want to say something to his younger self, this is what he would say:

chill out

don't stress so much

live in the moment

everything will be fine

be more of yourself

don't try to do what you think society wants or needs

don't try to live up to other people's expectations

self actualize

say no to more things

protect your time because it's very precious.

on your dying day you will give everything you have for another day.

the discount rate / marginal value of that extra day goes higher as you get older.

less fear, more love

love people more

everyone wants to be loved, everyone needs to be deeply loved

it's not something you can buy, no amount of money can give you true unconditional love

you can give love, it's free to give

you don't necessarily get it, but if you just get in the mindset of "I'm just going to give it", eventually, on a long enough time scale, you get what you deserve

just work on yourself and be ready, and then good things will happen

"when the student is ready, the master appears"