oneself / first-person pronoun: I, me (often shows the speaker's lower position in a hierarchy than the addressee) / (Kansai) you

myself, oneself

a photograph of oneself, a photographic self-portrait / (especially) a selfie

to take a photograph of oneself, to take a selfie

talking about oneself (especially, when the audience is not interested)

soul-searching

one's own concern or problem

(idiomatic) selfishness, self-centeredness

(Internet slang, derogatory) talking about oneself whenever possible; self-centered

to decide to do something: to do something on purpose / to perform a maneuver, to carry out a tactical action / to decide on an opinion: to believe in an opinion firmly