When you spend time with someone and then hear a rumor about that person, you are able to discern whether or not that rumor is true. If I were to hear a rumor about my wife, I would know whether it was true or false. Because of my relationship with Lisa, I have insight into the kind of person she is and the kind of character she has.
However, when we hear something about someone we don't have access to, or a close relationship with, we have nothing to measure the truth of the claim.
I believe one of Satan's greatest strategies is to blind us from the truth about how God sees us so that Satan can lie to us about who we are. When we spend time in the Word and we read about God's love for humanity and the sacrifices made, when we speak to God through prayer, when we listen for God's voice for direction...we are aligning ourselves with truth.
Without these things, there is space and opportunity for lies to fill our minds. Lies about who we are. Lies about the value we have. Lies about the direction we are going. Lies about how God sees us.
People believed the earth was flat, until the truth was discovered that it is indeed round. What lies do you believe? Do you even know they are lies? Begin filling your mind with God's Word and the counterfeit will become evident.