There are encouragement and a warning in these words in Galatians 1:10. And what is more, a direction for our lives! Mankind serves what is in his heart, and if that heart is stretching towards God, then God will be the witness. At the same time, if we lower our interests and are enticed into other delights, God is also the One who sees it first. We may be able to hide it from ourselves or others, but He who sees into the heart cannot be fooled.
In the end, we will never be held accountable unto beings lower than the Creator, so convincing others of our conviction will not do. We must actively demand that every corner of our souls are searched out in the light of Jesus, or fall under the judgment of the One who created us for Him