I was helped and encouraged by the following statment from John Barclay (Durham) in his explication of the relation of divine and human agency in Paul.
[A]n essential feature of grace in Paul's theology is its inherent subversiveness, its tendency to call into question the normal methods of reward or the expected channels of delivery. This is mirrored in (and no doubt partly based upon) his own life-story. There was none more successfully advancing in Judaism, fulfilling the traditions of the ancestors and excelling in zeal for the law and righteousness, as defined by that law (Gal 1.13-14; Phil 3.6). But his encounter with the grace of God was emphatically not another stage in that advance, a further refinement to the righteousness he found in the law, but a total re-evaluation of all his norms, an act of God which undercut what he had previously held to be the definition of piety. This is nothing less than an experience of death, a co-crucifixion with Christ. . . . Crucified in baptism, believers live only inasmuch as they share the risen life of Christ; 'under grace,' they can now identify the crucial weakness of the law which was fatally exploited by sin. The depth of despair about the self here is matched by the shocking exposure of the inadequacy of the law; the power of the flesh can only be countered by the power of something newly present on the scene, the Spirit of Christ.
--"By the Grace of God I am What I Am": Grace and Agency in Philo and Paul," in Divine and Human Agency in Paul and His Cultural Context (eds. Barclay and Gathercole; T&T Clark, 2006), p. 150