Always know and be able to articulate the reasons you have for making the choices you do.That's it. As I've written in the past, you hire brains, not bodies, so it's essential that these brains are switched on and doing what they do best. It's easy for anyone - especially as we become comfortable in our jobs - to kind of turn it off and fly on autopilot. But since knowledge workers essentially have been hired to think, if you go onto autopilot you're not doing your job anymore.
Note that the rule is to know and articulate your reasons, not anticipate what reasons I would come up with. That's a critical point. I don't have the reasonable expectation that nobody who works for me will make a mistake ever (and I wouldn't want them to be that cautious anyway), and I also don't expect anyone to channel my own decision making and become a Tim Callan satellite. Not only would these expectations be impossible to deliver on, but they wouldn't yield the best results anyway.
But it is reasonable for me to expect that you're always doing the best you can, that you're taking the knowledge, experience, and reason available to you and using them make the best decisions you're able to make. So long as the people who work for me are doing that, we're good.