성찰이 · 성찰을
reflection, introspection
Example
일기를 쓰면 하루를 성찰하는 데 도움이 돼요.
Keeping a diary helps you reflect on your day.
Word parts
성 examine+찰 observe
Literally 'examine and observe' oneself.
Good to know
성찰 is deeper and more philosophical than 반성, which usually implies regret over a mistake.