He also knows we'll fail - hence His Grace and forgiveness.
That's not to confuse Forgiveness of sin with Permission to sin, however -- as the homosexual community does. They operate not in the Repentant and Forgiven body of Christ -- but against that body in the spirit of anti-Christ.
Matt 5:17-20
17 "Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them. 18 I tell you the truth, until heaven and earth disappear, not the smallest letter, not the least stroke of a pen, will by any means disappear from the Law until everything is accomplished. 19 Anyone who breaks one of the least of these commandments and teaches others to do the same will be called least in the kingdom of heaven, but whoever practices and teaches these commands will be called great in the kingdom of heaven. 20 For I tell you that unless your righteousness surpasses that of the Pharisees and the teachers of the law, you will certainly not enter the kingdom of heaven."
NIV
No, He knows the flesh is weak and that is why He sends His Spirit of Truth to empower us, that we should not fail, that we should overcome the weakness.
“To he who overcomes”
“I can do ALL things through Christ who strengthens me”
And yes, should we stumble, we have Him as our advocate before the Father, however, stumbling is not something done on purpose, it is done out of weakness or ignorance and so when we have been made aware of that which we first tumbled, we should no longer stumble because we know how to traverse the path so not to stumble.
When we have been made aware of a commandment, and we understand what He says are the requirements of that commandment, if we break it, we do so by choice, not by weakness. And that is why James said this in Acts 15:
Act 15:21 "For from ancient generations Moses has, in every city, those proclaiming him - being read in the congregations every Sabbath." 22 Then it seemed good to the emissaries and elders, with all the assembly ...
Every Sabbath these new converts would hear Moses being read and so every week they would learn more about their contract with God and as they learned, they would apply what they learned. Moses is the school master, Christ is the Perfecter. We do not throw out what we learned from the school master, through the power of the Spirit of the Perfecter in us, we too can perfect that which Moses taught us.
Shalom