Long layovers go wrong in quiet ways. Nobody loses the whole window at once. They lose ten minutes finding baggage claim, fifteen minutes choosing food, twenty minutes waiting for a ride, and suddenly the city plan is gone.
Counting gate-to-gate time as free time
The clock starts after deplaning and ends before boarding. Everything else is a tax on the layover.
Choosing too many stops
Every extra stop adds walking, ordering, waiting, paying, and decision time. Pick the thing you would be glad you did even if it is the only thing you do.
Ignoring the return trip
The outbound ride is exciting. The return ride is risk. Build the plan around getting back calmly, not squeezing in one more photo.