They endured because out of love they obeyed the guidance of the Lord.
We work together, hand and hand, with the Lord our God for salvation. We are not puppets, and do not still have free will to chose. This and our Lord Jesus calls the Holy Spirit our helper, not controller. There will be some out their that will refuse the guidance and the power of the Holy Spirit, which is the unforgivable sin. It is only if your faith is rooted strongly in Christ, and you obey the guidance of the Holy Spirit and its working in you that you will endure.
Those who endure are the Elect. They are God's chosen. The Lord our God had chosen His people before they were born and before the foundation of the world. No man can repent and or be spiritually regenerated of their own power. No man can deepen his relationship with Christ by His own power. They need God to transform them and to help them to connect with the Lord. Does this mean God forces salvation on people? No, of course not. What this means is that God is aware of your future free will choices and He draws a person and grants them repentance. Somebody that God knows is wicked in this life is not going to be given repentance (Even despite God commanding all men to repent). In other words, you think it is primarily you who must overcome, when in reality is it is Jesus who works in you to do so. For Jesus is the author and finisher of our faith. But you would rather have me believe that it is you who is the author and finisher of your faith.