It is not incredibly hard because all I have to do is pull things from my memories of following baseball for almost 70 years and then use Baseball Reference to provide the details.
One of those memories involves the Mariners and Angels in 1995. That was a season that started a little late after the labor dispute that wiped out the last half of the 1994 season and the playoffs.
On August 20, the Mariners with a record of 53-53 were in third place 12.5 games behind the Angels, who led the second place Rangers by 9 games. The Mariners only had 2 remaining games against the Angels. Angels fans were probably thinking that all the Angels had to do was play .500 ball in their remaining 37 games and they would be in the playoffs.
What happened was that the Mariners went 25-13 the rest of the way (splitting their 2 games with the Angels):while the Angels went 12-25 and the teams ended up tied. The Mariners beat the Angels 9-1 in a playoff to win the division.
This is just one example. It can happen and it has happened, so people who remember it are going to be wary of something similar happening to their teams, even if it has a low probability, like losing a game after leading 10-3 in the seventh inning