All this 'find closure' stuff is said and written by people who feel uncomfortable around other people's grief.
On the other hand, we do need to adjust to it, so life is bearable. When my sister died, I had an irrational desire never to see the first agony of grief go away. She was so special to me the idea of this agony going away, seemed to say, I no longer cared about her. But even as I thught this I knew I was being irrational. I could not have lived with it long term, it would have killed me.
So I think what we do is we earn to live without that person. Easier with a sister than a husband, because we lived some distance apart so were used to being apart. For someone you have lived with, with love for decades, that is something else.
But, the grief never goes. We are downsizing and moving house and our household goods include things that previously belonged to my sister and, even these many decades later, as I resolutely give them to charity or send them to auction, I mourn.