While they are surely major factors, it is perhaps not only safety of comfort or the fear of the unknown. Other factors could be:
Sheer laziness
Lack of motivation
Too rigid an attitude

I suggest by rank ordering these- and possibly more factors- we get real clues as to what is bogging us down. This would be the first step towards planning and taking purposeful actions to overcome them.

You and I agree that no one else motivates us.

When called in by organizations to train their leaders when teaching at York U, I share that we must change our non-serving thinking so that we can refocus our behaviour by motivating ourselves.

When leaders see their team members doing the same inappropriate things over and over again, the need is not to harangue more (i.e. what many teach, incorrectly, will motivate others). Instead, we need to ask ourselves: “How am I letting that one, or them, down?”

Best regards,
@GaryFPatton