Safe designs employ strong-versatile materials to withstand edge cases, pre-failure signals to alert users, prevention-interruption mechanisms to avoid/stop cascading failure, designed-failure points to prevent catastrophic failure.
Example: Material. Metal gears last a long time. Weak plastic gears can strip under high torque, crack when cold, and warp when hot.
Example: Signal. Smoke alarms beep on low battery. Hard drives slow down before they fail. Car dashboards show engine problems.
Example: Prevention-Interruption. Circuit breakers shut down the main electrical connection when high current is detected. Lock-out Tag-out procedures prevent people from turning on equipment when someone is working inside it.
Example: Designed Failure Points. Car crumple zones are designed to break and absorb the impact force of a crash, destroying the car but saving the passengers.