There are many ways that Satan seeps into our lives and tries to control us. Often, they appear through our thoughts. The enemy often uses lies to convince you that you should sin.
A way to steer you from Christ is to tempt you into sin. Hearing a voice in your head saying that a sin is not a big deal is a common way Satan tries to deceive you. After convincing you to sin, you may feel immense guilt and shame instead of going straight to God for repentance and forgiveness. Satan wants to steer your thoughts away from God to destroy you.
When you find yourself saying “God will never forgive me” or “God doesn't love me,” that is a tactic to make you question your identity as well as God’s identity, using your shame against you. This can easily develop into insecurities and doubt in God’s character. His character is kind and loving, and He doesn’t count faults. Contrary to what the enemy tries to claim, God does not keep count of our sins.