Someone will read your memoir pieces and will ask when and where and how these pieces came together. You will write one piece today, the next one a month or two from now, or even decades later. What and how you write will be influenced by your mood, your health, your other conditions. Your reader may not know that your piece about your husband was written after he became ill, after you and he separated.
Establish the here and now in a couple of words and a couple of details.
"As we watched the ocean on a warm June Sunday a few weeks ago, your father with a blank canvas trying to capture the waves, I thought about how far away you all were, how busy and exciting your lives were. I remembered how we all celebrated Father's Day when you were little, the times at Disneyland. At that time I thought how extravagant ..."
I set up the time and the place and the emotional state of my present before I relive a Father's day of your childhood. This is important for my children to know for two reasons, how they remember the day versus how I remember it, and my status when I wrote this.
I was conscious of this when I wrote my memoir, and established right away that I was an old lady and had one grandchild at the time of the writing.