Thresholds

Each stat and skill is governed by a threshold that determines the "range" that you can obtain. Doing things related to the stat/skill gives you experience, the more "extreme"/difficult the act (and in the case of some stats, such as fetishes, the more public the act is), the more experience you will gain. As your stats get higher "simpler" acts will give less or even no, experience.

Certain key events in the story/quests will unlock new thresholds that will allow you to increase your stat to new levels. If your current stat is below your new threshold you will get automatically "caught up" to the minimum value for that threshold, after which experience proceeds as usual.

To learn more about specific thresholds, check the stats page