expressing regret for doing wrong or not doing something

expressing remorse, regret

shy (the usual word)

shy

(especially of a woman) pretending to be shy, modest

very modest

not having, not showing, much belief in one's own abilities

hesitant; unconfident

showing that one is inferior, less able etc

meek, unassuming

having, showing, a low but honest opinion of one's own merits, abilities etc; not large in size or amount

shy

(especially of hair having a dull brown colour; (of a person) timid, shy

drab; quiet

showing respect

courteous, mannerly

(of a person) self-conscious and uncomfortable in the presence of others; (of animals etc) easily frightened

quiet and self-conscious

not drawing attention to oneself; modest

shy

not too obvious or easily noticeable

keeping a low profile

not selfish

kind, giving