Dealing with backstory

It can be so easy to fall into the trap of writing too much backstory. Aren't we all a product of what has gone on before in our lives? Therefore, it would follow that our characters are the same.

Liz Roberts who whittled down the Debut Dagger entries – ‘Many entries started off very well – and then ran the reader into the literary equivalent of a brick wall around page 3 or 4, because they couldn’t resist putting in a lot of backstory.’

The best piece of advice I have read came from literary agent Carole Blake in From pitch to publication -
'In order to illustrate a character trait, or a backstory element, demonstrate it with a scene, a snippet of dialogue, but don’t have the narrative address the reader like a newsreader reading facts.'