Why is it that when things go wrong it all happens too quickly to process, let alone stop?
If seeing miscellaneous relative's corpses littering the pathways of the Uchiha estate had been the icing on the cake to his youth, then running home in a state of terror only to find the brother you idolized was the murderer had to be the cherry on top. Too bad Sasuke had never really cared for sweets, and that his whole world had done more than turn upside down, his reality had inverted entirely.
In the days, weeks and months that followed that encounter Sasuke Uchiha's mind twisted and turned on itself, he was truly and hopelessly alone in this world in ways no other soul could possibly understand. The dark-haired child hardened his heart and set himself to a singular purpose, vengeance. He would make Itachi pay for what he'd done.
It had been years and his sole purpose had been diluted by friendship and superficial bonds with his peers. How could he have turned a blind eye to his goal?!
So he left, he needed power. Orochimaru could give him power, he knew that to be true.
How could one possibly become Hokage if they can't even save one friend?
If growing up orphaned, unwanted and rejected by not only your peers but the older generations as well had been the broth in his ramen, then the pain and humiliation during his failures after he graduated the academy were the noodles themselves. Suddenly Naruto didn't want to touch his beloved ramen again.
In the time following Sasuke Uchiha's departure from Konohagakure Naruto Uzumaki spent more time pouring over his failures that was healthy for anyone, weeks faded into months as his tear ducts threatened to dry up from overuse and friends stopped visiting so much as demanding he move on and do something about it. How could he be Hokage if he couldn't save one friend?
So he left, he needed power. Jiraiya could teach him power, he knew that to be true.
Who would believe you love him if you are too weak to fight in his name?
If watching helplessly as the love of your life leaves the village and becomes a rogue ninja was the icing on the cake, then the pain that she'd placed on her remaining teammate's shoulders was the cherry topping it all. Settling into a numb routine, Sakura wished she'd never loved at all.
In the years following his misguided abandonment of his duties as a ninja, Sakura Haruno had refused to truly let herself fall into despair. She fought long and hard to improve her abilities, trying desperately to catch up to her male comrades, but she always fell short of their natural ability. How could she say she loved him if she could not fight in his name?
So she stayed to become powerful. Tsunade could unlock her power, she knew that to be true.