Memories are triggered in many different ways. Sometimes it is when you smell a fragrance your friend used to wear. Or maybe a bad smell of food (cooked cabbage) that reminds you when your mother MADE you eat it.
Some memories are triggered by sounds - especially music. I think most of us have vivid memories from our teen years or when we fell in love for the first time.
Each of us has good and bad memories. Hopefully, it is the good ones we hold on to and let the bad ones go. But both types of memories have triggers.
And then there are pictures. Pictures of when we were children. Pictures of our first date, dance, or graduation. Pictures of long lost friends or family members.