I'm not sure what you mean by "sadness". I assume that you used this word to differentiate this feeling from "depression". Did you mean a sorrowful feeling related to some specific event such as the loss of a loved one? For me, sadness never goes away. I may forget about a particular sadness for a brief period. But as soon as the memory returns, so does the sadness. They are inextricably linked. I suppose that, over time, the "sting" of the sadness lessens a bit. But, sometimes I even wonder about that. Maybe others have a different experience.