Grand strategy political micromanagement game, you will understand that Arbitrary Rulers can do whatever the hell they think they want. Sending roses for a neighbor, ending up taking care of the garden.
Marriages for political reasons, alliances because the enemy of my enemy is my friend, duchies stronger than kingdons, kingdons that might rise out of nowhere, you will learn that family members are actually your worst enemies (not that different from nowadays I think) and you will lose battles, win wars, learn how grateful you were for making friends, and how stupid you were for not realizing someone else's friends are really powerful.
Educate your brood, rule over the vulnerable, offer protection and prey on the weak, intrigue and plot over claims, create claims with your court, become a paragon of virtue and control a religion, call holy wars on infidels, kill your enemy on battle, kill your enemy on an ambush, become friends with your fellow neighbors, walk the lands as looters for money and supplies.
Spread your dynasty around the world, spread your seed around, deal with invasions from the west, invasions from the east, revolts, religious zealots with massive armies spreading havock over your lands, learn that the real use of religion is for politics, learn that children can be conditioned.
Change history, create empires, destroy mighty foes, rise the ladder of the prestige, be envied by your enemies, die in the annals of nowhere, if you become incapable watch as your regent push laws and change things as he sees fit.
Play online with your friends, same kingdom or different kingdoms, be kind and deceitful, be cruel but just, be a jerk, be a leader, be yourself, be your character but always remember: Real world will never be the same once the feudal knowledge affects your judgement.
This game is a training for fatherhood.
Also, watch out for the Game of Thrones MOD