I reply that I feel great and that being lean feels great. But that's not the whole truth.
People with a remote interest in fitness and health usually aspire to get lean and maintain that condition. They may also assume that reaching a satisfactory or awe-inspiring condition will elevate their lives to a new level. Much like people assume that winning the lottery will make their lives indefinitely better in just about every aspect.
In striving towards this goal, some people have an ideal body weight in mind. Others may have a mental image of their physique or an arbitrary body fat percentage in mind. Goals may vary a lot but expectations do not. Once the goal is reached, everything will be great.