So it's not ok to do hill repeats on a climb, or stop to look at the scenery, take pictures, or just misjudge your effort and need to recover?
There are numerous reasons someone might pass you and then slow down.
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You could fall off a cliff and die.
You could get lost and die.
You could hit a tree and die.
OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.