God has not given you a spirit of fear (2 Timothy 1:7). This doesn’t apply to certain fears only—it means any fear. It means the fear of messing up, the fear of lack, the fear of failing, the fear of being ridiculed, the fear of not finishing.
God has not “assigned” those things to you, so when they appear in your thought life, you can take a step back and recognize them for what they truly are. They have been sent by another source, a source other than God, which means you don’t have to listen to them or believe what they are trying to tell you.
Fear cannot be trusted. It is not a reliable source of information.
If you’re dealing with fear as a writer, take it to God. Sit down with Him and your journal and work it out. Listen to what He says about it and look in His Word for answers. God wants to be your help, and you and your book are safe with Him.