A recent conversation reminded me of something I think I first noticed during the years when I was questioning my religion:
Often the hardest part of thinking outside the box is realizing that there's a box you've been thinking inside of in the first place.
Applications of this idea:
It can help to ask yourself every once in a while, what boxes might you still be in where perhaps until now it hasn't even dawned on you to question whether there might be an alternative perspective?
It reinforces the benefit of seeking out and listening to very diverse perspectives, even (or especially) those you disagree with or from people who see things very, very differently than you do. I find it really eye opening to try to see something from a really different perspective. Often extremely hard, but very eye opening and (for me, at least) endlessly fascinating.
It can help people feel more empathy towards those who don't think outside the boxes that outsiders clearly see.