Keep all the rules, still lose

Gal 3:19-25
19 What purpose then does the law serve? It was added because of transgressions, till the Seed should come to whom the promise was made; and it was appointed through angels by the hand of a mediator. 20 Now a mediator does not mediate for one only, but God is one.

21 Is the law then against the promises of God? Certainly not! For if there had been a law given which could have given life, truly righteousness would have been by the law. 22 But the Scripture has confined all under sin, that the promise by faith in Jesus Christ might be given to those who believe. 23 But before faith came, we were kept under guard by the law, kept for the faith which would afterward be revealed. 24 Therefore the law was our tutor to bring us to Christ, that we might be justified by faith. 25 But after faith has come, we are no longer under a tutor.

Imagine a person was able to keep all the rules - to follow God's laws fully and completely - always, without failing once. A perfect law-keeping record. That's impossible, of course, but even it really did happen this person would still be far, far away from God because there is no Life in the law. In fact, in order to have Life, we had to die to the law. Unless a person dies to the law, he or she cannot be raised to Life with Christ.

Rom 8:2-3
2 For the law of the Spirit of life in Christ Jesus [true Life] has made me free from the law of sin and death [God's laws]. 3 For what the law could not do in that it was weak through the flesh, God did by sending His own Son in the likeness of sinful flesh, on account of sin...

"Weak through the flesh" doesn't mean that we were weak because of all our bad deeds. It means that even in the best of the best of our own righteousness (the ability of our flesh), we were still dead. We were weak and fell short of God's glory (and Life).

What we needed was the gift of Life, not law.