Negativity.

Yesterday we were practising Isabellas lines and she got them all right. The trouble is I have noticed that she doesn't like to be right all the time. What I mean by this is that even when she has done something right she likes to say "But I nearly forgot it, or I nearly got that wrong" as if she likes to be negative. I am not sure if this has something to do with not wanting any attention for being good or whether she wants attention for being bad. Does anyone have any suggestions. I am trying to get her to understand that she needs to feel proud of herself if she does things right.