It is clear that if someone is a true religious or a true person of prayer and aims to enjoy the delights of God, he must not turn his back upon the desire to die for God and suffer martyrdom.
For don’t you know yet, Sisters, that the life of a good religious who desires to be one of God’s close friends is a long martyrdom?
A long martyrdom because in comparison with the martyrdom of those who are quickly beheaded, it can be called long; but all life is short, and the life of some extremely short. And how do we know if ours won’t be so short that at the very hour or moment we determine to serve God completely it will come to an end? This is possible.
In sum, there is no reason to give importance to anything that will come to an end. And who will not work hard if he thinks that each hour is the last? Well, believe me, thinking this is the safest course.
Saint Teresa of Avila
The Way of Perfection, Chapter 12

Kieran Kavanaugh, K, Rodriguez, O, and Teresa, 1976, The Collected Works of St. Teresa of Avila, ICS Publications, Washington DC.
Isn’t this the 2nd Reading for the Office of Readings for the Martyrs of Compeigne? Am wondering since the beginning of the reform of St. Teresa who were the first nuns ever to suffer martyrdom.
Great question! To the best of our knowledge, the first martyrs among the nuns of the Teresian reform are the martyrs of Compiègne.