We are not left to our own resources!

Christians can only persevere through the power of God. Left to themselves, to their own strength, to their own resources, they would undoubtedly fall away and lose their salvation. But God will not permit this to happen to those who are his own, whom He has chosen in Christ from the creation of the world (Ephesians 1:4) and whom He predestined to be conformed to the likeness of His Son (Romans 8:29)... this is the heart of the teaching (of perseverence & preservation)... believers persevere only because God in His unchangeable love enables them to persevere.

--Anthony Hoekema