RobH_en_tn/luk/21/14.md

Therefore

"Because of this," referring to everything Jesus has said, beginning in Luke 21:10. (See: rc://en/ta/man/translate/writing-connectingwords)

resolve in your hearts

Here "hearts" is a metonym for people's minds. Alternate translation: "make up your mind" or "decide firmly" (See: rc://en/ta/man/translate/figs-metonymy)

not to prepare your defense ahead of time

"not to figure out ahead of time what you will say in order to defend yourself against their accusations"