Copy and pasted from /a/nime.
Shinji's mind was unable to understand the difference between shape (God's creation and the outer appearance and other's perception) and image (one's own perception); the ideas that he was taught and given to him by society were simply seen as the truth without giving that truth an image. Since Shinji saw truth as this, he was unable to form his own image and only saw himself as other saw him, thus he was dependent on the praise of other and could not bear the consequence of failure.
He began to see that his image was tainted by the ideas of other and Shinji's shape. He then begin to realize that he is capable of having subjective thinking and view the world in a slightly skewed image. After realizing this, he sees that the World around him is not cruel and bad, but that is due to viewing the World in that manner; if Shinji imagined his World in a slightly different manner, then his image would become much more positive and become more optimistic of his life.
The hatred that Shinji had for himself (created from his shape) was the reason that he had no image of reality; he needed to learn that ideas taught to him are only one person's perception of truth and is not absolute truth. In order to overcome that and begin to form his own image of truth, Shinji needed to realize this. With the help of the image of the others close to Shinji, he saw that the truth of the World is not grand and the rule of One, but rather an almost insignificant view of reality. Once Shinji saw this, he realized that the image of others should only be used to help form the image of self and not define it. Coming to this epiphany, he is able to shatter the ideas of his mind created by others, and gave Shinji the will to form his own image and path and life.
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I posted this because I actually LIKED the TV ending of the series. Shinji's teenage angst is what really drew me to the series. No, really. The fighting angels in giant mecha part was just a treat. So with TV Ep. 26, Shinji found self-worth in himself and that was the resolution to his angst. Which is why I liked Evangelion.