Christ's Resurrection works in virtue of the Godhead; now this virtue extends not only to the resurrection of bodies, but also to that of souls: for it comes of God that the soul lives by grace, and that the body lives by the soul. Consequently, Christ's Resurrection has instrumentally an effective power not only with regard to the resurrection of bodies, but also with respect to the resurrection of souls. In like fashion it is an exemplar cause with regard to the resurrection of souls, because even in our souls we must be conformed with the rising Christ: as the Apostle says (Romans 6:4-11) "Christ is risen from the dead by the glory of the Father, so we also may walk in newness of life": and as He, "rising again from the dead, dieth now no more, so let us reckon that we (Vulgate: 'you')" are dead to sin, that we may "live together with Him." [ST III Q56 A2; emphasis added]
But our works do not cause the resurrection of Christ. Therefore our works do not cause our justification, and furthermore the Gospel proclaimed by the Catholic Church is not "works-based" as is erroneously suggested by some.
St. Thomas continues:
Two things concur in the justification of souls, namely, forgiveness of sin and newness of life through grace. Consequently, as to efficacy, which comes of the Divine power, the Passion as well as the Resurrection of Christ is the cause of justification as to both the above. But as to exemplarity, properly speaking Christ's Passion and death are the cause of the forgiveness of guilt, by which forgiveness we die unto sin: whereas Christ's Resurrection is the cause of newness of life, which comes through grace or justice [ibid., ad 4]
Again we see that justification is entirely the work of God, not of man.