“Take care, brothers, lest there be in any of you an evil, unbelieving heart, leading you to fall away from the living God. But exhort one another every day, as long as it is called today, that none of you may be hardened by the deceitfulness of sin.”

Like the Prophet Amos, the writer of Hebrews presents a warning to his audience, composed primarily of Christians who had converted from Judaism. They held Moses and their ancestors whom he had led out of Egypt in high esteem. The writer reminds them that, despite the fact that the Lord had blessed His Chosen People with great blessings, spectacular miracles and mighty acts of deliverance from their enemies they still chose to rebel against him. They lacked faith in Him and so perished in the wilderness, never having entered the land the Lord had promised.
The reason the writer brings this up is that many in the audience were being tempted to go back to following the Mosaic Law. They thought this might make life easier since they were enduring persecution from both the Romans and the Jews. The problem was that following the Law meant they were rejecting the sacrifice of Christ to trust in the Law and works for salvation. There is great danger here for those who went back to the Law would be guilty of hardening their hearts against God as did the ancient Israelites. They would suffer the same loss of the promise.
Those who persevere in the faith of Christ do not they earn their salvation by their perseverance, suffering, or good works. Rather their salvation is demonstrated by their perseverance and by deeds of faithfulness and righteousness for such are produced only by the power of the Lord. He works through the Holy Spirit and through the church as well, so we need the body of Christ, our fellow believers, to encourage us in our struggles and to hold us accountable for our actions. Together we choose daily to walk in obedience to the Lord and to believe that He is able to do all He has promised. This does not mean we are perfect nor that we never fall, but we press on by the power of Christ in the midst of chaotic times.