Time is a duration measurement.  It is precious because you only have so much of it.
The main thing that really perplexes me about time is that it goes quicker as I get older.  No one has been able to offer me a reasonable explanation of this phenomenon.   I remember being in grade school waiting for the 3:00 bell to ring.  2:50-3:00 seemed like an hour.  3 months summer vacation seemed to last years.
one reason it goes by as you get older - your live is very similar and your mind timestamps large amount of time as thoughts. you were at the same job for 6 years and lived in same home for 10 years - your mind/memory compresses many thought into a blur 
so - move around, have lots of lovers, do new challenging shit - your mind will compress the same memories into a blur. 
my 2 cents....
the older i get (34) the more i take awesome care of myself (sunscreen, flawless keto diet - with some cheating) but being healthy buys you more time (less sick, feel better) tons of water, etc
i do like a vodka martini and a cigarette but very rare now  
also living below your means buys you time too. you have more freedom with less financial obligations and poor decisions - less stress.  
also the calendar itself has changed over the years, i think were 10 days in a year back before the french made it 7 days a week