An interesting post arguing that in almost every instance flashbacks ruin fiction, (https://warriorwriters.wordpress.com/2015/06/12/why-flashbacks-ruin-fiction/). Do people agree?
I use flashbacks in my book, “Samantha” to explain how Sam becomes embroiled in the world of forced prostitution. None of my reviews mention my utilisation of flashbacks so, in the case of “Samantha” they where, I hope employed successfully.
K Morris - Poet 
Flashbacks, along with flashforwards, are a great thing, as they convey timeless ideas and concepts instead of permitting characters’ experiences to distract from the truth.