I myself; oneself; by oneself
Emphasizes that the speaker or subject does something personally, often with a sense of self-awareness or contrast to others.
I did it so well that even I was surprised.
It has become a habit without him even realizing it himself.
even I; even oneself
Adds the nuance of 'even' to the reflexive pronoun, often used when the speaker is surprised or when including oneself in a statement.
Even I can't believe it.
自分でもわからなくなってきた。
Even I'm starting to not understand.