How many times in a given day or week do you feel a little unsteady?
For example, you think you're fine on level ground, but then you get on escalator and you spend the ride trying to stay balanced. You don't actually tip over or anything, but you just have that vague feeling that you might.
Or you look at an escalator with all your luggage and think " you know what I think I'm gonna take the elevator."
Or, you are putting on a pair of pants and your toe briefly gets caught at the bottom of the pants and it almost knocks you over.