There was only one child that ever obeyed His Father perfectly. Our spirits may be willing ... but our flesh is weak. Try as we might, we all fail from time to time. I am not condoning sin. I'm simply admitting it ... and acknowledging my need for God's grace given us in Jesus Christ.
Stumbling at times does not mean one does not continue to be obedient.
For the one who is obedient in the faith to the Lord when they do stumble they will admit/confess that sin for forgiveness and turn away from it.
But now if one continues in that sin (continues to constantly be disobedient) the bible shows they will not be saved and receive eternal life for they are trampling the Son of God underfoot.
Luke 12 and Hebrews 3-4 show what happens to those who are continuously disobedient to His teachings, and it shows they will not enter the kingdom of heaven and will be appointed with the unbelievers.