Situational awareness probably works well 95-98% of the time.
But walking into a dark building from blinding sunlight, or into a mini-mart that has reflective film on the windows can still put you into a poor or bad situation.
Knowing some self-defense moves always seems better to me than not knowing ANY self-defense moves.
Your legs are longer and stronger than his knife arm. Fold his knee the wrong way and his focus will change dramatically.
Sue