I did that early on with my favorite La Leche League leaders. I invited them early, into my super-ego, to talk to me when they weren't there. 🙂 Trying to keep their voices in my head made me remember that I wouldn't want to do things that would keep them from feeling good about my progress and their assistance.
I think it's the purpose of saints (imagery in the house or worn on the body) or amulets or other religious or superstitious objects. I mean I think it's natural and ancient, among people, to have absent witnesses. The feeling that ancestors can see what we're doing is common in some cultures (and, honestly, ours—it came up at my house on Tuesday at a memorial for a dead friend, even though most there were atheists; it can be soothing, and inspiring).
photo by Jihong Tang