The futher your enthusiasm is away from 5, the quicker it drops/rises back to 5. e,g, It will take a day to drop from 13-12 but it will take a week for it to drop from 6-5.
After a match playing TIE it's not unusual to see enthusiasm at 12/13, but come next match day it'll drop back down to 10 for the game.
Just remember that teams out of the Cup race only have 2 opportunities to TIE in a week, instead of 3. (scrimmages are always played on normal). This might explain the difference for some teams