feel ashamed, shy
愧 centers on a painful self-awareness of one's own shortcomings or wrongs: feeling ashamed, embarrassed, or shy because of a sense of having fallen short.
愧 combines 忄 (heart/mind) with 鬼, which likely contributes the sound and may suggest a ghostly or fearful quality to the shame. The exact historical development is uncertain.
The heart radical 忄 beside 鬼 (ghost/demon) suggests a heart haunted by a ghost of past actions, making you feel ashamed and shy.
For キ, imagine a key that unlocks a hidden shame: key -> キ, and your heart feels the weight of that shame.