WARNING: The following contains spoilers for Boruto: Naruto Next Generations Episode 168, "Training Begins!" now streaming on Crunchyroll.
Recently in Boruto, Sarada's had a tough time with her lack of confidence in her abilities. It doesn't help that she and Team 7 got pummelled by Kara's Joker, Deepa; a fight which left Mitsuki clinging to life. She and Boruto knew as soon as they recovered, they had to go back to the drawing board because they didn't just see other nations' shinobi killed, they witnessed their own seniors Mugino and Konohamaru also getting brutally beaten.
As Boruto trains with Kakashi, Sarada's inspired to train with her dad, Sasuke, in the latest episode. And as they go through the motions, it's revealed why she's the weakest of all the Uchiha clan, which has to do with her Sharingan conditioning and peaceful upbringing.
The Sharingan is an ocular dōjutsu that only a Uchiha can be born with. For centuries, it's given them an advantage in war since being passed down by Indra Ōtsutsuki, son of the Sage of the Six Paths and Kaguya's grandson. But it's only activated by powerful emotional triggers. Sarada activated her single tomoe -- tomoe being the marks within a Sharingan eye -- when she saw Sasuke, excited as he was gone from Konoha for years doing Ranger work. But things like this don't happen often, especially as the family's much all together now.
Conversely, Sasuke describes the other side of emotional triggers, where severe trauma, distress and pain lead to Sharingan evolution. Negative triggers are more common and often have to do with the Uchiha "Curse of Hatred," which takes root when an Uchiha sees or hears about someone dying, or when they themselves kill someone. It occurred with the likes of Madara, Obito, Itachi, Shisui and Sasuke to name a few, and Sasuke tells Sarada she can't train her eye unless she goes through something similar.
In the past, the Uchiha were the military force of Konoha and had child soldiers fighting wars from an early age. Thus, they'd evolve their Sharingan much quicker, making them prodigies. Sarada wants to be one but her dad insists she can't short-circuit it. Ironically, in an era where the Great Nations get along, where war is scarce and young shinobi don't train as extensively or have deadly missions, and where there's no infighting in the village, Sarada just doesn't know hardship like her father did. So this is a double-edged sword because she's in a comfortable, safe and sound, but this time of peace hinders her progress.
Sasuke does make it clear she should work for progress without tragedies to drive her, though, teaching her to streamline the current vision she has with her lone tomoe where she has to dodge metal slugs thrown at her. However, as she exhausts her eye and it bleeds out, Sarada doesn't want to give up, which worries her spying mom, Sakura. She knows her daughter's placing a lot of pressure on herself, especially as she and Sasuke are the last of the Uchihas. It's clear, however, Sarada is actually light years ahead of someone else who'd have this handicap at her age and Sasuke's assured her she's on the right track as she isn't complacent.