The reading of hexagram 51 is unusually narrow, and its narrowness is what makes it useful.
The figure describes a sudden event that arrives from outside, frightens everyone, and passes. It says almost nothing about the event itself. What it addresses in detail is the querent's conduct during it, and the instruction is consistent across the lines and the judgement: do not drop what you are holding.
That is the sacrificial spoon and chalice image, and it is not a counsel of stoicism for its own sake. In the situation described, the ritual continues and the person who keeps their grip is the one who is still functioning when the noise stops. The second line's advice about the lost treasure makes the same point in another register: do not pursue it, and it will return in seven days. Chasing the loss is the error.
The hexagram's other consistent note is that fear is appropriate. The first line has shock followed by fear followed by good fortune, in that order. Nothing here suggests the querent should be unafraid; it suggests they should be afraid and steady, which is a considerably more achievable instruction.
The inverse figure is hexagram 52, Keeping Still, and the pair sets movement against immobility as the two responses to an unstable situation. Read together they are the book's fullest treatment of the question of when to act, and each is impoverished without the other. Both are doubled trigrams, which the tradition takes as showing their principle undiluted, and the sequence places them side by side so that the comparison cannot be missed.