Short answer: Everything you say and think, according to the Testimony of God, is not a sin.

There have been false teachings perpetuated in some sects of Christianity that promote the idea that everything (or almost everything) you say or think is a sin. In fact, the Word spoken by the apostles often spoke of liberty even going so far as to say, “All things are lawful for me, but all things are not expedient” in 1 Corinthians 10:23.

The reason Paul can make that statement is because he obeyed the commandments of the Son. Commands of the Son are pretty simple: Love His people according to His example [John 13:34] and repent (turn from sin) with our faith toward Him. So, what exactly is a sin and what should we repent from? It is detailed here.