I found this under Rules>Tactics:
Enthusiasm
You can decide how hard you want you team to try on any given day (except in a scrimmage, where your team is just going to try as hard as they normally do because the coach is watching). Your team has a baseline level of enthusiasm that they bring to the game, and the more enthusiastic your team is, the harder they will be able to play. You can also tell your team to try harder in an important game (Crunch Time), although they'll need some time to recover over the next week or two. Alternatively, you can Take it Easy in a game so that your team will be able to play harder in the future. In addition, your team's enthusiasm tends back towards the default value of 5 over time, and will always reach 5 during the offseason.
For particularly important games, including league playoff games, relegation games, and the final two rounds of the national tournament, your players will be too excited to "take it easy". In these games, the only options available are Playoff Normal, in which your team receives the enthusiasm effects of a regular Take It Easy but the effort level of a regular Normal, and Playoff Crunch Time, in which your team receives the enthusiasm effects of a regular Normal but the effort level of a regular Crunch Time.