To live a life worth living, you must know Jesus is the truth and Satan is a liar. Until you understand this beyond an intellectual level, you will struggle and continue to live an ineffective life for the Kingdom of God. Every sin, every distraction, every temptation in your life started with you believing what the devil told you. Let me assure you, as the father of lies (John 8:44), everything coming out of his mouth is a lie.
You never should wonder if it might be true, it isn’t. Conversely, anything Jesus says is an absolute and undeniable truth. You never should wonder about this either. Jesus is the truth and Satan is a liar.