"There's nothing special about Sakura Haruno. For the first thirteen years of her life, that's what she heard endlessly, it's what she lived and fought and knew to be true. In a village with so many prominent and powerful clans, with so many kekkai genkai, secret and special jutsu, and so much importance placed on the clan you come from...Sakura was born without a clan. In a world that idolized powerful and notorious ninja, her father never exceeded genin, and her mother's shinobi career ended in her first skirmish in the Second War.
As far as any children in the Academy were concerned, Sakura was a child of either civilians or failed shinobi...and none of them would ever settle on which was worse. As a young child, Sakura had no special talents that made her stand out amongst the teachers of Konoha. Although she could easily knead chakra and learn jutsus, her ninjutsu skills were weak and taijutsu pathetic. Perhaps even worse among the kunoichi in training, Sakura's hair color stood out, while her face...did not.
The only thing important about Sakura Haruno is how big of a forehead she has. The only things that made Sakura stand out among her class were her hair, the size of her forehead, and how overwhelmingly average she was. As a child, Sakura was quiet, and followed her father's advice to try to avoid conflict...and that quiet timidity made her an easy target for the cruel children in the Academy. As time went on and the children grew more persistent, Sakura began to shy away from any physical training or jutsus and teachings that required physical demonstrations, rather being late than making herself a target for jeers and heckling. Although she focused on keeping up her grades through excelling on written tests and book learning, her jutsu knowledge became theoretical and her chakra pool remained miniscule.
All told, the bullying of Sakura Haruno lasted for three years, from when she first joined the Academy at three, until the frightening and dominant Ino Yamanaka befriended her at six. Although no longer actively bullied, stage whispers of the useless girl with the abnormal forehead continued whenever the blonde wasn't present, and the idea that Sakura Haruno shouldn't pretend to be special persisted.
Sakura adopted the tough and defiant attitude of her best friend, and copied the girl's keen sense of fashion to protect herself from the ninja failure that was Sakura Haruno, but her attention remained on the fashion and building up her self-confidence and self-image, instead of ninjutsu or taijutsu training, and so her knowledge remained only textbook.
At the age of eight, Sakura experienced her very first crush, on one Uchiha named Sasuke. Sasuke was attractive, quiet yet driven, and everything in a shinobi Sakura wasn't. Because of that, she wasn't the only one in the class to fall for the Uchiha clan's youngest heir. The disdain of the friends Ino had brought her made her cling to the idea of the young Uchiha even more tightly. So tightly, in fact, that when her friend Ino revealed she too had feelings for him, she couldn't bear to let go and accept the Uchiha heir was beyond someone like Sakura Haruno even for Ino's sake. She transformed her friendship into rivalry with all the self-confidence she'd learned to imitate.
As it turned out, the Uchiha heir really was beyond someone like Sakura Haruno.
When the Hokage-apparent hand-picked new genin for his team, the heirs of the Uchiha, Hyuuga, and current hokage were chosen. The girl without a clan was not.
Sakura Haruno never intentionally gave up on her feelings for the Uchiha heir, but she did give up hope on them. Although the end of her pursuit of Sasuke also meant the end of her rivalry with Ino, so too did she lose her self confident bravado.
In the end, Sakura Haruno ended up on Hayame Shirakumo's team, alongside Kiba Inuzuka and Shino Aburame, clan-heirs with less pull to their names than the three in the Hokage's team, and no family legacies to secure their place like Team Asuma. Shirakumo was a strict and practical sensei who had little taste for either self-pity or heroics. The first order of business was to hand out chakra paper to each of his students and determine their nature. Sakura's paper turned to dust.
Shirakumo would have nothing of Sakura's quiet intentions of fading into the background of the team, insisting that if she didn't contribute to the team, she needn't be a shinobi at all. Once instructed, Sakura took well to kenjutsu, not requiring the years of ninjutsu training she had shirked during her years of bullying in the Academy. Although Shirakumo was one of the leaf's rare Wind users, a nature opposite and unrelated to Earth, he nevertheless taught Sakura what he could of his advanced nature transformation skills, and where his sword strikes blasted slicing air at his opponents, Sakura learned to use the sword as a shield and an imprisoning claw, enhancing her strikes in ways that allowed her creativity and intelligence to thrive.
Sakura Haruno was not among the Rookie Six who attended the chuunin exams in her first year. Sakura and team Shirakumo took the chuunin exams when she was fifteen, and passed easily.
During the finals of her chuunin exams, she caught the attention of one Shisui Uchiha, who could discern her until then undiscovered aptitude for genjutsu (or perhaps he simply admired the skill with which she used the body flicker technique taught to the team by Shirakumo, himself a renowned Body Flicker user, Sakura was never quite certain). Either way, shortly after receiving her Chuunin flak-jacket, Shisui approached her and offered to tutor her in genjutsu.
It's been a year since she's started training her genjutsu skills under Shisui, and while she has always been efficient and skilled at chakra manipulation, it's genjutsu where her true talent lies and the 'special' in Sakura shines. Combining the kenjutsu and earth release learned from Shirakumo, the genjutsu techniques studied with Shisui, and the body flicker taught by both, her skills have jumped by leaps and bounds and the 'normal' Sakura Haruno has been greatly increasing in rank and status since becoming Chuunin. Some believe, as she's given more high-profile missions due to her unique combinations of skills, that the late-blooming chuunin of her class might be one of the first to make Jounin."