fear
慄 centers on a visceral, trembling fear: the kind of dread that makes one shudder or quake.
慄 combines 忄 (heart) with 栗, which likely contributes both sound and the idea of trembling or shuddering, as 栗 can suggest a shivering sensation.
The heart radical 忄 beside 栗 (chestnut) suggests a heart trembling like a chestnut shaken from a tree: 慄 is the fear that makes you shudder.
For リツ, imagine a fearful person who lets out a trembling 'rits!' sound when startled: rits -> リツ, and the heart shudders with fear.