no having flashback is actually a normal occurrence for humans. associating a persons memories with the present moment is just a part of how the brain works. one way to familiarize yourself with this is sit in a very public place and listen to those around you. you will hear people say things like OMG that reminds me of when..... hey doesnt that look like....its just part of being human to have our senses alerting us to things we remember from the past.

just today I was at the coffee machine at work and the smell of the coffee reminded me of waking up in the morning to my mother making the morning coffee. for a minute there it was like I was back home in bed, waking up to the smell of my moms coffee which is a very happy/fond memory of mine.