In "Biblical Perspective" R.E. Trotter writes:
Jesus made it clear to each of the seven churches that a life of victory was required of each of the saints regard-less of how impossible their situations seemed (Rev. 2 and 3). Even when Satan was cast out of heaven and came down to earth with great fury to attack the saints, “they overcame him by the blood of the Lamb, and by the word of their testimony” (Rev. 12:11). Overcoming is the normal standard for all Christians and a requirement for keeping one's name in the Book of Life (Rev. 3:5).
Source: Christ, the Triumphant Lord: Adult Teacher's Insights, page 71.