Clinging to the Character of God

Hebrews 6:9 Even though we speak like this, dear friends, we are convinced of better things in your case—the things that have to do with salvation.10 God is not unjust; he will not forget your work and the love you have shown him as you have helped his people and continue to help them.11 We want each of you to show this same diligence to the very end, so that what you hope for may be fully realized. 12 We do not want you to become lazy, but to imitate those who through faith and patience inherit what has been promised.
The writer of Hebrews penned some hard words - that some within their group had turned their backs on what they had been taught, and were trusting instead on works and rituals and not Christ.  But he knew many of them were not. He was clinging to the the justice of God: He will do the right thing when He judges. He knows hearts.  There was evidence that they were true believers, and that evidence was their reflection of God's character, in the attribute of mercy.  The assurance of salvation is a tricky thing, as Jesus pointed out. Those who thought they were "good" and "in", like the self-righteous leaders, were not.  Those who really seek after God can at times feel they are not good enough (non of us are).  It all comes back to the character of God. He is merciful, forgiving, and Holy (among other things). Are we? We are to reflect His character as part of our trusting in and following Christ.  There is a balance: not being confident in ourselves, but humbly trusting Him to be Who He really is.