Had a few instances of this:-
1. Playing top of the table and with 10 men we were 60-4. Lad at 5 scored 80 in about 10 overs, guy at 6 who hadn't scored a 50 in years, belted a ton and I chipped in with a cheeky 50. Highlight was seeing there faces when I dumped the leggy into the trees to bring up the 300 for 5. We had smacked 240-2 in 30 odd overs. Declared soon after out of pity and they came nowhere close.
2. Played in a t20 final. Opening bat for us hit the first ball of the game out of the ground, but we quickly collasped to 24-7 in 8 overs. From 27-7 off 10, we hit 84 in the last 10 to scramble 111 in 20. Oppo were 50-1 off 8 and fell away to 99-7 off 20. Totally mentally shot.
Point of both games is when you let it slip that badly you rarely recover. The team that gets away with it often lifts their game, while the team on the receiving end just subside. Moral, if any, is to finish strong. Just don't get yourself in a hole you can't dig yourself out of.