One funny thing about situational awareness is that when you lose it, you don't always know, because, well, you've lost your SA.

Put differently, something you consistently find when you postmortem incidents where people have lost their SA is that they thought at the time they had full SA. They only notice they've lost it when things are clearly going downhill.

So it's important to regularly re-ground yourself with reality even if you think you don't need it. That's a critical component of maintaining SA.