The claim ‘we are what we do’ is still unable to establish an identity between our person and our actions. For the first ‘we’ from the sentence suggests the possibility of being different from our deeds, though such possibility is abolished.
Meanwhile, the contrary affirmation - ‘we are not what we do’ – exposes itself to be contradicted by every action we do.
In the first case, our identity is recognized as a vague idea which makes the transition to the actions. In the second, it is firstly stated as a firm idea, but becomes weak after its contradictions.
So, if we pretend to be masters of our actions, our identity involved into them is either vague or weak. Therefore, it is not surprising that most of our successful actions follow in fact the social habits, while the really personal actions often fail.