I think of sitting on a tree by the creek on the farm. The cattle are grazing in waist high grass in the pasture and my horse is nuzzling my shoulder with his nose. It helps me relax before I sleep to remember it in as much detail as possible.
I think about what happened that day! Also I try to think if there was anything I forgot to do. Think also of things I need to do the next day! Sometimes I pray for a family member or friend! Or I just think about things that make me smile like flowers and pink things, funny jokes I've heard or sing songs in my head that will relax me!