People who are good at grieving, those who recover from a trauma or a massive loss - they grieve and feel it deeply but then turn away from the negative feelings.
They accept and move on, they don't ruminate or over-think on the negative and pessimistic.
Over thinking ushers in a host of adverse consequences. It sustains or worsens sadness, fosters negatively biased thinking, impairs a person’s ability to solve problems, saps motivation, and interferes with concentration and initiative.
Moreover, although people have a strong sense that they are gaining insight into themselves and their problems during their ruminations, this is rarely the case. What they do gain is a distorted, pessimistic perspective on their lives. Sonja Lyubomirsky