Mattie and James are in love. But too many mornings and too many miles apart have taken a toll on them. As they struggle with the distance between New York and Chicago, their visits become reminders of the difficulties, not the pleasures, of their relationship. Joe Swanberg and Greta Gerwig follow with “Nights And Weekends,”an intimate portrayal of longing and confusion. This time Swanberg co-stars with Gerwig, and Gerwig co-directs with Swanberg, creating a film that resonates deeply and leaves scars that fade but can’t heal.