I think Julius Caesar lived his whole life, believing (or at least acting) like he was invincible.

He gets captured by pirates, and he incessantly demands they treat him with respect and that he is going to come back and crucify them. They don't kill him, and he later comes back and crucifies them.

During his Gaul campaigns, he would regularly be in the thick of the fight, and several times came close to being killed.

During mutinies, he would regularly go out among the mutinous soldiers without really a whole lot of protection and talk them down. He could have been easily killed during that time.

So what we see as complacency or fatalism, may just be Julius Caesar acting like he always did. That strategy had worked his whole life, until at the end, it didn't.