HMMMmmm...
I thought it was UNBELIEF that caused the losing...
You didn’t lose your sinful standing outside of Christ because you did good deeds did you? Why would you lose your righteous standing in Christ because of the sin of unbelief?
God fully judged and condemn all sins of everyone including unbelief past, present, and future on the body of Christ on the cross 2000 years ago. How could God condemn your sin of unbelief now if he already judged that same sin 2000 years ago? That would be unrighteous double jeopardy and God is not unrighteous.
As you were once born into sin as the seed of Adam that you yourself could not change, so now, you are born again into righteousness (righteousness is a gift, not what you do (Rom. 5:17)) as the seed of the Second Adam that you yourself cannot change. Once you are born again as God’s child, you are forever saved “to the uttermost”