We dare not be cavalier when it comes to hearing from God. In other words, we can not assume every word is from God. Our flesh will often try to influence us in a way that although may not seem counter to God's word, it very often has ulterior motives.
Years ago someone we knew said that our flesh was the enemy in the camp. My understanding from that statement was that the flesh can not to be relied upon, as it will ultimately try to please itself first. This is why God's word implores us to be cautious and suspicious of the flesh. Peter tell us that the flesh wages war against the soul, so it is not to be treated casually.
The soul is open to vicious influence from spirits that are against God and man. They seek to destroy and alter our belief in God through our mind, will, and emotions. Their hope is to snag us into believing a lie, which is anything that does not line up with God's word.
One way to test the spirits is to hold them up to the true nature of God, and if they do not pass this scrutiny then they are likely false. This becomes my litmus test, whether real or not, for I am not drawing my strength to discern the counterfeit spirits alone, but through the infallible power of the Holy Spirit. It is the Spirit of God that is my greatest ally when the enemy comes calling.
1 John 4:1 NLT Dear friends, do not believe everyone who claims to speak by the Spirit. You must test them to see if the spirit they have comes from God. For there are many false prophets in the world.