Reformers believe that perseverance is both commanded and absolutely necessary in order to get into Heaven. We do not take it lightly.
However, it is not your perseverence, at least from what I gather. According to my understanding of reformed theology, man plays no part, it is ALL God. That would be where we disagree, the "all" part. It would be senseless to be commanded to do anything if we didn't have the ability (with God's aide) to do it. All wisdom, for example, comes from God. But He willingly GIVES it to those who ask. Thus, it is indeed OUR righteousness, given to us by God.
That is my take on it.
Regards