Continuity mistake: In the scene where Bruce is fighting in the restaurant with the other chinese guys, his shirt is stained with dirt in the back. The amount of dirt on his shirt changes from shot to shot.
Continuity mistake: In the gym fight, Jason Scott Lee takes his left sock off when getting ready to fight. In the next shot he takes the same sock off again.
Continuity mistake: When the demon slams Bruce's head against the tombstone the final time, the blood splats on the tombstone before Bruce's head hits it, and before the sound effect for the impact is heard.
Continuity mistake: Bruce lee fights with Johnny Sun for the first time. At a certain time, Bruce is laying on the ground and kicks Johnny on his shin/ankle. He kicks on the front so Johnny should fall towards the ground with his front. However, you can see Johnny falling flat on his back.
Answer: His belief in a family curse.
Captain Defenestrator