God seems to be suggesting this in Deut 30 and in Genesis where Cain is told that he can overcome sin.
Deut 30 says that man has the power to turn to God, but, then, it is God who will turn your captivity. In other words, man calls upon God, and then God releases you from the captivity of sinful desires.
vs. 30:6 "And the LORD thy God will circumcise thine heart, and the heart of thy seed, to love the LORD thy God with all thine heart, and with all thy soul, that thou mayest live."
In the old testament, it was promised to the Jews that, if they turned to God, God would not only 'circumcise
their hearts', but also bring their people out of bondage from the surrounding nations and into the Holy Land of Isreal.
However, today, since the Jews did not follow God, they have remained scattered, as God said would happen. Israel now is the Church, which shall be gathered and brought to the promised land, the New Jerusalem, when Christ returns to judge the entire world. Those who keep the commandments of God while in exile in this earthly life among the nations who now control the world will inherit the Eternal Kingdom when Christ returns to dash the nations and establish Himself as King over all the earth. That is the Christian understanding of Deuteronomy 30 in combination with the New Testament writings.
As far as Cain goes, if Cain had repented, God would have rendered him a participant in His righteousness and given him the strength to overcome sin. As it stands, Cain despaired over himself and used that despair to justify his continuation in sin, for he told God that his punishment was too great for him to bear.