If you put a tube, patch kit, tire boot, mini pump, mini tool, in a small seat bag its always there when you go ride. Nothing to think about, hassle with, or forget.
All that can also fit in a jersey pocket, but then you got to grab all that stuff and put it in the jersey.
Just leaving it with the bike is easier IMHO.
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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.