Not every such grace converts: the ineffective desires
Thesis VI. They do not, however, claim that this grace proper to Christ always actually converts a person and produces true and earnest repentance in him. For someone moved by it does not always will or do, effectively and fully, what ought to be willed and done.
A sinner often gets stuck in the merely ineffective desires that grace has shaped in him, and through his own weakness and fault does not carry them through to the deed. He may even cast those desires aside, and as concupiscence fights back and wins, fail to turn from sin, or to repent as he should and as much as he must to rise from sin and receive God's forgiveness.
Latin
VI. Neque tamen eorum mens est, propriam hanc Christi gratiam hominem semper actu & reipsa convertere, & poenitentiam veram ac seriam in eo operari. Idque quoniam homo ea gratia motus, non semper vult aut agit efficaciter & perfecte quod volendum & agendum est: & saepe contingit hominem peccatorem in solis inefficacibus desideriis quae gratia efformavit haerere, nec ea ad operis effectum ob infirmitatem suam ac vitium proprium perducere; abjicere etiam desideria ista, & reluctante ac vincente concupiscentia, non resipiscere a peccato, non agere poenitentiam ut oportet, & quantum oportet ut a peccato resurgat, illiusque veniam a Deo consequatur.