How to deal with this negative copycat personification of you? Imaagine this voice as a person. Now put your arms around this person - or shake their hand - and say "I've got this now," and tell them to walk back to where they have been living in your brain and close the door. They may say "but...but...I want to save you from making a mistake." You just tell them that mistakes are part of writing and not to worry.
You see in our first draft work all we want to do is get our words/story down on the page - digitally or on paper. When we go through that first draft we see places we need to fill in, or change scenes, or add details to the story. Or we might want to even put our chapters in a different order.
This is part of the process. Our negative lodger doesn't know process but you, wonderful writer, are learning about the process and you make your corrections as you go along.
There is no such thing as writer's block there is just too much listening to our negative lodger - just keep going even when the screen seems blank. Begin with these two words: and then...and it never fails to unlock whatever you have been thinking about. Really. It works every time.