I feel as if my 'mother' job is done. My children are now adults so I limit my worrying. I enjoy their company and the love and affection I receive from my grandchildren is priceless.
They all know that I'm here and will help if I possibly can. Basically, though, their problems are their own - either to solve or learn to live with.
My daughters do find one of my DILs 'difficult to get along with' 'very hard work' etc. but I've told them to make allowances and make a big effort to stay in touch and meet up.
After all, it benefits all the children to have that close relationship with their cousins. The children's future is far more important than petty squabbles, unkind remarks or hurt feelings.
I am friendly and close with them all, encourage them to visit, take care to be neutral and never criticise. If any complain about another, I'll point out the other's point of view and any potential problems/difficulties they may have. I won't be drawn into bitching about them - very important!