Overwhelming grief at loss of family unit

[curlychocs]

7 weeks into separation due to DH affair. Marriage is done, he still with her and that won't change. However, I cannot stop feeling overwhelming grief that we are no longer one family unit. It doesn't help that I have a stepdaughter who is struggling with it all and is wanting to split her time 3 ways which is very difficult.

How do I mend this? How do I get over this grief?

Time. With time you adjust to being a new family unit. You and your DC, plus other adults in their lives, GPs, aunties, uncles, good friends.
Mum, dad and DC together is just one model but others can be as secure and fulfilling, if not more so. Families also evolve over time as children grow, leave, bring in partners, gaps are closed and others open.
The key to some of this really is to try not to think too hard about what you don't have, and make the best of what you still do.