In Hattrick, overconfidence is an event that happens when a team severely underestimates their ]series opponent and thus performs worse than it normally would. This usually happens when a team leading the series is playing a team in the bottom part of the table. Overconfidence does not happen in cup or friendly matches.
The overconfidence check is done once before the match; if there is overconfidence, there will be a message about the players' attitude before the match begins. The affected teams's midfield rating is halved. It is possible for the coach to try to amend the effects of overconfidence during the match break, which is mentioned in the match report at the beginning of the second half; this only happens when the overconfident team is losing.
Based on some research, overconfidence can happen when a team with a strong or better confidence plays a team at least 6 places below it in the series table. It is not clear yet whether winning streak is a factor, or if the number of psychologists is, although many web pages suggest that psychologists should be fired in cases where possible overconfidence can lead to problems.
In some cases, overconfidence is not much of a problem because the winning team would win anyway; sometimes, however, an overconfidence event could decide to whom goes the series medal.