The one and ONLY person to judge yourself against
As human beings, it seems to be in-built into our nature to compare ourselves to others. To rank what we have against what another possesses, in whatever capacity - 'Oh, that person has a really nice car', 'She can sing so much better than I can', 'I wish my hair was naturally curly like that'. This is never truer than when we compare our bodies to someone else. 'I wish I had legs like hers' or 'I want to be skinny like Keira Knightley', 'Why can't I look as good as . . . . '