Enthusiasm
Enthusiasm indicates the level of interest a Sim has in a particular hobby. By interacting with objects associated with hobbies, a Sim can increase their enthusiasm and unlock new interactions. Sims will occasionally dream about their hobbies, and these dreams will raise enthusiasm by a small amount.
Sims that are really enthusiastic about a hobby can get "in the zone". When their enthusiasm has reached the maximum level and they are performing an interaction related to that hobby, they will forget about everything around them. Sims "In the Zone" have a glow surrounding them, and if their hobby is Music and Dance they'll hear an audience clapping. The first time a Sim reaches maximum enthusiasm in a hobby, he or she will receive Lifetime Aspiration points. Sims may also have a major want to reach maximum enthusiasm in a hobby.
Enthusiasm will gradually decline over time, so Sims will need to perform hobby-related activities to maintain their enthusiasm levels.