My experience is that most people are even less likely to share freely and easily in subsequent relationships, often feeling they have been betrayed or distrusted before.
It takes a huge amount of trust to be able to share your innermost feelings with another don't you think? As my wise friend describes it...to start to trust another is like slowly getting undressed in front of them. some things are easy to be honest about, others we show and then quickly cover up again. There can be false starts...and going quickly doesn't equal reaching truth any faster...it's a process that takes time, patience and unparallelled honesty and trust.
I think it's important to maintain privacy...we don't have to share every single thought or detail of our lives...and what is shared in confidence needs to stay in confidence...but i do think it's vital to be honest and true with the information we do share. An opinion given should be the true one...a reaction should be a heartfelt one.
If it's true that we uncouple because of a secret I wonder does it then stand to reason that we have the best chance of success when our relationships are devoid of secrets?