Invincible Position

Why did the two people who thought they would stay together for a lifetime studying in a foreign country become like strangers after returning home? Is it really that difficult to fall in love and stay together? Why do women often play scheming in order to remain invincible in love? Why do women just want to be undefeated and not feel heartache? Why do they return home completely defeated? The man has always adhered to his principles and no longer loves her, so why can't he help caring about her and loving her. In the end, only loving each other can make you invincible. Happy ending.