cheerful
惔 centers on a bright, warm inner state: cheerfulness or light-heartedness. The single given meaning 'cheerful' captures this directly.
惔 combines the heart radical 忄 with 炎 (flame). The structure suggests a heart warmed by flames, giving rise to cheerfulness, but the exact historical development is uncertain.
The heart radical 忄 beside 炎 (flames) paints a picture of a heart glowing with warmth. Imagine a cheerful person whose heart is lit up like a cozy fire.
For タン, picture a cheerful person getting a tan by the fire: tan -> タン, and the warm flames match the heart's cheerful glow.