I haven't had any terrible mistakes, but I had a week where I couldn't do anything right last year. One of the games I was defending a 2-1 and the guy went to pass it across, I turned it went off my foot and right past the goalie. Another one was I threw a pass across the ice in my own zone (yeah bad idea), I passed it, and the pass was right on the stick of the winger from the other team, came down and scored on a breakaway, I got ripped on the bench, my coach flipped. What made it worse was that it was against my rival school.
I've tripped over the blueline on a 1-1, the guy didn't score at least.
I had a breakaway, the puck went on an edge and I shot it and it went about a foot wide of the net.
Whiffing on a slapshot is a bad feeling also.