Do not be deceived. We reap what we sow. There is a law of nature that involves sowing and reaping. A farmer sows the seed and expects to reap a harvest. That is also a spiritual principle. We reap what we sow. That's the reason Scripture says, "Do not be deceived, God is not mocked; for whatever a man sows, that he will also reap" (Galatians 6:7).
A person without Christ continues to sow to the flesh, which is the corrupt nature of those who reject the grace of God in Christ. They are deceived by the works of the flesh in their unbelief. While a believer sins from time to time, he cannot continue in sin without the discipline of the Lord (Hebrews 12:5-11). Believers repent and confess their sins to find fresh cleansing in the blood of Christ (1 John 1:7-9).
Do not deceive yourself. "For if anyone thinks himself to be something, when he is nothing, he deceives himself" (Galatians 6:3). If we think that we are above temptation, we deceive ourselves. Every believer faces temptation from time to time without exception. Yet, we can depend upon God to help us when tempted (1 Corinthians 10:13).
Do not be deceived by false doctrine. Salvation is not by grace plus our works. To the contrary, salvation is by the grace of God, through the finished work of Christ. It's through Christ crucified for our sins and risen for our justification. It's Christ working in us. We are his workmanship as a new creation in Christ. "For in Christ Jesus neither circumcision nor uncircumcision avails anything, but a new creation (Galatians 6:15).
