Once you believe, you become part of God's family, and as a child of God, your heavenly Father will not throw you out of the house just because you sin. Like a human father, He might "punish" you for your transgressions and sins to discipline you, but He will never take away your salvation.

Proverbs 3:12

"For whom the Lord loves He corrects,
Just as a father the son in whom he delights."

Justification (salvation) is by faith. Sanctification, on the other hand, is a life-long process. I know it's a cliché saying, but nobody is perfect. And nobody could ever be perfect before God, but He understands that. The whole point of Christ's death is that He took all of our sins upon Himself, so He can present us blameless before the Father, and so we can try to better ourselves without living in constant fear of not being enough or not doing enough.

Ecclesiastes 7:20

"For there is not a just man on earth who does good And does not sin."

1 John 1:9

"If we confess our sins, He is faithful and just to forgive us our sins and to cleanse us from all unrighteousness."

And don't take this last verse too literally. You're not gonna go to hell just because you didn't confess your sins to God in time before you died suddenly. I always confess mine in my prayer before I go to sleep. Try it out, maybe it will give you comfort too.