(I don't find this to be a philosophical question, I find it to be a psychological one. So I am going to give a psycho-therapeutic answer, which is by necessity mostly opinion.)
What is the real motivation for 'overcoming' sorrow? What does this actually mean? It implies that sorrow is some kind of domineering enemy that is by design intended to limit us. Those are the kinds of things that one overcomes.
But sorrow is an evolved response. It has a purpose, or it would most likely not persist across a wide swath of the evolutionary tree. It is therefore not likely to be maladaptive in a real, natural state of existence.
So what is the objective effect of sorrow? What are sad people better at? Sad people are more realistic about the effects of their actions. They have temporarily suspended the optimistic bias that comes naturally to animals. Presumably, a period of greater realism has some way of protecting or developing them, if one presumes that emotional reactions are evolved to preserve a species.
Having lost someone upon whom one had a certain level of dependence, may require seeing many things in a more realistic light. The intrusion of negative options might be an opportunity to really weigh them objectively against our usual reality, which has a positive bias.
Like all emotions, we can become too comfortable with a given state, or too prone to enter it. But I think we defend ourselves against emotion too forcefully, and not realistically enough. We should not dwell in and depart from the world when we are scared or sad, because we are in doing so preventing any learning. Earlier generations of humans simply did not have our level of safety and could not do this if they had wished. The demands of life were more urgent.
But we should not be focused on getting away from or doing away with negative emotions. We should be focused on engaging the world in all our different internal states, and paying attention to how things are different.