In Dirac's book on GRT, he says the following, p. 45: "In curved space the conservation of energy and momentum is only approximate. The error is to be ascribed to the gravitational field working on the matter and having itself some energy and momentum." Yet when I work my way from the Schwarzschild metric to the geodesic equations, one of them produces the conservation of angular momentum. There is no approximation that I am aware of. What am I missing? Was Dirac wrong? Can anyone explain? Thanks.