τοὺς ἐν δυνάμει θεοῦ φρουρουμένους διὰ πίστεως εἰς σωτηρίαν ἑτοίμην ἀποκαλυφθῆναι ἐν καιρῷ ἐσχάτῳ.This is taken by Arminians to indicate that we keep ourselves by our faith. If we disbelieve, we are lost.
The emphasis on the crucial nature of faith is clearly based in the text. Any teaching that makes faith non-essential is clearly not apostolic, and thus not Biblical. But the Biblical question Calvinists always pose is, "And where does a spiritually dead, God-hating rebel / dependent saint get that faith, and persevering grace?"
Peter gives the answer here. The Greek text makes it fairly clear (at least to me) that the ideas of keeping and believing are not to be divorced. It isn't as if God keeps us a little (or a lot) by His power, and we keep ourselves a little (or a lot) by our faith.
Rather, we are characterized (τοὺς) as those who are "by-the-power-of-God-kept-through-faith-unto-salvation."
Must we believe? Yes. How do we believe? By the power of God. It is how God keeps us by His power: through faith.
Thus, properly viewed, preserving and persevering faith no less than saving faith is part of the "all things" that God gives us as a result of Christ's work on the Cross (Romans 8:32; cf. Acts 11:18; 13:48; Ephesians 2:8-10; Philippians 1:29).