Doing it scared vs. doing it stupid

[Emily Simmons]

One of those inspirational FB memes came up in my feed yesterday, and it's basic sentiment was that at some point, you just have to do it scared. Take the leap of faith. And I appreciate that kind of encouragement. But at some point, your fear is actually warning against doing something stupid. So in terms of REI (and especially for beginners who haven't leapt at all), how do you know you're doing it scared and not doing it stupid?