Be good to yourselves. If you have a negative inner voice, confront it, care for it, help it heal, whatever you need to do. So much of the doctoral journal is done in isolation.
When I was in first grade, my teacher made a note on my report card. It said, "Prefers to work alone."
Still true. However, when the voice in my head gets going, it isn't always kind. I'm working on it. As you move ahead in this journey and spend a lot of time with yourself, be working on your self-talk as well. You can call it imposter phenomenon or whatever you want.
The truth is, you can do this. It's hard, but many good things are difficult. Some bad things are difficult, too - but that's not the point of this post.
One of my favorite comics is Dinos and Comics. Here's one that might be helpful. Be nice to you.