決心
けっしん · kesshin · JLPT N3 · noun
resolution
✊❤️ 決心 = decide + heart: your heart has decided
決 means decide or settle (as in 決定, decision) and 心 means heart or mind. A heart that has decided is resolve. The reading kesshin comes from kets(u) + shin: the tsu sound doubles the s that follows it.
心 — pictograph of a heart with chambers and aorta
心 is a pictograph showing a stylized heart, with strokes representing the organ's chambers and the aorta at the top. Originally meaning the physical heart, it broadened to cover mind, feelings, and intentions, since ancient Chinese thought located thinking and emotion in the heart.