"We must catch up soon!"

It's a phrase near universal in adult friendships - a text we've likely both sent and received.

We mean it in the moment, with the best of intentions. But between work, family and endless to-do lists, a simple catch-up can become a logistical nightmare.

Yes, we must. But we rarely do.

It explains why research finds we lose around half of our friends every seven years.

It's not that we're suddenly "fundamentally incompatible", says psychologist Dr Marisa Franco, but because relationships shift as life stages change.

Be it moving in with partners, getting married, focusing on our careers or starting a family, friendships become "the easiest place for collateral damage" for both men and women explains author Dolly Alderton.

The question becomes how to maintain the same closeness with less time together.

Relationship expert Claire Cohen, author of BFF? The Truth About Female Friendship, who recently had a son is experiencing this first hand.

She's found herself in "identity limbo" between her old friends and the new group of mums she's met through antenatal classes.

Claire says she wants a fully rounded group, not just people who know the "new me".

To fix this, she's become more transparent, vulnerable, and creative in........

© BBC