Consider this quote from Herman Bavinck (1854-1921), a Dutch Reformed pastor and theologian:
In [Roman] Catholocism there are always two kinds of Christians: those who occasionally go to confession and mass, observe the required fasts, and for the rest live quite a superficial, carefree life, trusting in the Church for their salvation; and those who are dissatisfied with such externalities, and attempt to life a purely religious life through mysticism and asceticism, in separation from the world and denial of the flesh, thus to come before the face of God. Far be it from us to immediately denounce the latter with Protestant judgment that since such piety issues from a false principle — righteousness by works — it is therefore worthless to God. For no matter how much truth that judgment may contain, before we utter it we must remind ourselves that the Catholic righteousness by good works is vastly preferable to a Protestant righteousness by good doctrine. At least righteousness by good works benefits one’s neighbor, whereas righteousness by good doctrine only produces lovelessness and pride. Furthermore, we must not blind ourselves to the tremendous faith, genuine repentance, complete surrender, and the fervent love of God and neighbor evident in the lives and works of many Catholic Christians. The Christian life is so rich that it develops its full glory not just in a single for or within the walls of one Church.
Nevertheless, Catholic piety, even in its best form, is different in character from that of Protestantism… Complete inner certainty of faith is lacking. It always leaves room for the question: have I done enough, and what else should I do? Rome deliberately keeps the souls of believers in a restless, so-called healthy tension. Spiritual life fluctuates between false assurance and painful uncertainty. ~Bavinck, The Certainty of Faith (bolded section mine)
Here is a link to this book:
And I found this quote in the preface to this: