When God created Adam and Eve, He had hoped to establish a relationship with them for eternity. When they were obedient, they stayed pure and undefiled in the garden (Gen.2:8). When they disobeyed God, the end of their eternal life and the corruption within them began because of their knowledge of good and evil (Gen.2:17). They were banished from the garden and they and future generations, meaning us, could no longer be with God like before. This was how sin began and separated us from God (Isa.59:2).
Now, the knowledge of good is not the knowledge of God. When we know what is good, we may try by our own will and strive in our own strength, to do ‘good’. This can become a heavy burden to carry. Being religious is like that; doing good to appear good instead of becoming righteous according to God by the conviction of the Holy Spirit. Jesus calls this hypocrisy (Matt.23:25-28).
The knowledge of evil works like this; when we know what is evil or bad, we are somehow tempted to choose it. Many people know telling lies or stealing is wrong, but they still do it! That was what Adam and Eve did; they knowingly acted on the thoughts that were contrary to God. Evil is manifested by disobedience; an unwillingness to listen or follow.
Whether doing good or evil, both are set in motion by our own desires, by our own self-will and not by God’s will. The sin within us is when we choose to do what we want, instead of surrendering ourselves and do what God wants.
Jesus said that from within the heart of men proceed evil thoughts (Mk.7:20-23). This is where the battlefield is, where we must bring the thoughts of our hearts that are contrary to God to the obedience of Christ and the word of God (2Cor.10:5, John.1:1).
He that is within us that is greater than he that is in the world is the Holy Spirit (1 John 4:4). He helps us in the battlefield to overcome sin when we allow Him or allow the Christ within us to be risen (Gal.4:19, Eph.4:13).
Jesus didn't do what He wanted. He did what God wanted Him to do (Luk.22:42). God has a will for each of us, a purpose for which we are made and it is His hope that you will come to that knowledge and fulfil your calling (Eph.1:18, 4:4).