The phrase in statu viae is used often by von Hildebrand in Transformation in Christ (TC). I found this phrase described somewhere by St. Thomas Aquinas as “the condition of those who are working towards the Beatific Vision, but who have not as yet actually arrived at it.” Therefore, this state of life applies to everyone who is still alive on this earth. I suppose it also applies to the souls in Purgatory, having not yet attained the Beatific Vision, but their metaphysical reality (which is different than those of us who are still alive) isn't applicable to a discussion of TC.

This phrase is contrasted by von Hildebrand with another similar phrase status finales: being the point at which we achieve our desired end – everlasting life with God in Heaven. These two phrases first appear early on in the first chapter of TC under the section subtitled: Moral progress requires unqualified readiness to change. Below is a quote from the beginning of that section.

But the unreserved readiness to change, as here outlined, is not merely the condition for embarking on our journey towards our supernatural goal. It also constitutes the permanent basis for continual progress on our road. It is an attitude we must always preserve so long as we are in statu viae – until we have reached the safe harbor of the status finales, where there is no longer any task proposed to our will, and where our souls will rest unchangeably in the boundless bliss of communion with God. Should that readiness to change and that passionate will to surrender ever cease, we would no longer have the proper religious disposition. That unlimited readiness to change is not only necessary for the transformation in Christ: even as such, it represents the basic and relevant response to God.

With this in mind we can never content ourselves with just “going through the motions” of our Catholic Faith. You can go to Mass everyday of your life but if it brings you no closer to Christ then what is the use. Although, if you really did go to Mass everyday of your life I don't know how you could be completely unaffected and not come closer to Christ. Nevertheless, the important thing for us is to foster and maintain this “unreserved readiness to change” within ourselves as we progress towards our goal of eternal life with Christ. In fact, it is the means by which we will ultimately, with God's help, reach the status finales.