Asuka's self worth is tied directly to her skills as an Evangelion pilot. Aside from being intensely proud of being the pilot of EVA-02, she's proud of achieving the highest synchronization scores. She constantly wears her interface headset to remind everyone of her status as a pilot and when asked, she says she pilots the Evangelion for her own self praise.

To further her pride, Asuka volunteers for the risky missions or positions and dislikes having to fight alongside EVA-00 and EVA-01. She prefers to do battle on her own, feeling that anyone else will only slow her down and impede her performance. Her pride is based on her being the absolute best at what she does and needing backup or having to work with others implies that she's weak. She reluctantly accepts help in situations that absolutely require it but when Shinji saves her, she's determined to return the debt rather than just accept his help. Being saved by Rei is even worse for Asuka, as she feels that Rei is the worst of the pilots; if she has to be saved by someone inferior, what does that say about her?

Asuka's so tied up in how others see her that her self-image becomes synonymous with EVA-02. When Shinji achieves a higher score than her for the first time, her self-confidence starts to fall. Despite Shinji only achieving a higher score once, it's enough for Asuka to feel threatened. She still has very high scores herself but can't handle the idea of Shinji beating her. After all, she's trained hard and he's barely trained at all! When Shinji gets attention for his accomplishment, Asuka begins to get bitter. She needs the spotlight to validate her self worth.

Thus begins Asuka's downfall... when she is unsuccessful in defeating Zeruel, her confidence drops even further. The fact that she couldn't handle one Angel on her own is devastating to her and she becomes increasingly distracted. Her sychronization scores begin to plummet and when the next Angel, Arael, attacks, she's told to provide backup to Rei in EVA-00. Being backup to the inferior pilot is unthinkable to Asuka and in a last ditch effort to try to redeem her pride, she disobeys orders and enters battle ahead of EVA-00. She's caught directly in Arael's mind-probing attack, suffering great mental anguish as she's forced to relive her childhood trauma. This mind-rape is one of the final straws for Asuka's confidence: after the Arael is killed, she becomes severely depressed and is unable to pilot EVA-02 any longer.

If Asuka cannot pilot an Evangelion, she feels that she is worthless. These feelings are validated in the next Angel attack where Rei is in dire circumstances and needs help. Commander Ikari sends Asuka out in EVA-02 as cannon fodder. When she cannot make her Eva move, she's withdrawn and Commander Ikari sends out EVA-01 to save Rei instead. Asuka is deeply wounded by this; EVA-01 was in lockdown and the Commander wouldn't send it out to help her when she was being mind-raped by Arael... yet he would send it out to help Rei.

Without the ability to pilot the Evangelions, Asuka is left without an identity. Nearly her whole life has revolved around her abilities as a pilot so with that taken away, she has nothing left. She even goes as far as running away and trying to kill herself because she has lost all desire to live.

When Asuka finally breaks free of her depression, it's clearly because she realises that her mother has been with her inside EVA-02 the whole time. Her mother tells her not to give up and she responds, perhaps indicating that she's realised her identity goes beyond being an Evangelion pilot.