3 levels of chess

I've been playing chess for about two years now, and i've come to realize there are 3 aspects to this game. The first 1 is learning and understanding the movements of each piece, the second aspect is strategy, why and when to move a particular piece. Now the last 1 gets complicated, it's what I like to call the "unknown". It's a secret only known to masters and grand masters alike, and the reason i say this is because i've watched many games played by grand masters, courtesy of chess.com and i just cant figure out why they move the way they do. The sacrafices they make, attacks with their king, things you cant find in a book. Ive seen them resign in games that i thought could be played on, but im just a beginner so i guess i wouldnt understand.A game thats been around for thousands of years how does one truely master in a lifetime. I've become over taken by this non-violent board war and im determined to conquer it.