The key to recording a good lesson is to record one thought at a time. What that means is just press record. Once you're recording, you are creating. You'll make mistakes. Dogs will bark in the background. All sorts of stuff will get in the way, but as long as you're recording, you can shrug those off and re-record that thought.
After you press record, just keep the recording going. If you're interrupted or anything happens, just let it run. Let yourself gather your thoughts. Take a deep breath. Then record the next thought. The main thing here is to focus on one thought at a time.
What I mean by that is stop and think, "How am I going to say this next thing? How am I going to type it?" Then type it out and say your thing. If you screw it up, you've just got to undo, undo, undo. Then try again and try again and try again. Use as many takes as you want on that one thought.
Once you get to the end of the thought, pause to think. The great thing about recording is that it doesn't matter how much empty space you leave in there. Deleting a big one minute chunk of you sitting there thinking takes one second.
Just take your time. Stop to think, "What am I going to say? What am I going to type? What is this next thought, this next step that I'm going to put down in this video going to be?" Lastly, don't worry. Be happy. This simply means you're going to need a ton of takes.
In my recordings, I have way, way, way more mistakes than actual good content in my raw videos. My raw, unedited videos are embarrassing to watch. They are terrible. They are full of crap and mistakes and noises, but the beautiful thing about videos is that you can edit them.
This is not a live presentation. This is not you standing up in front of a room of developers, doing live coding. This is a safe environment, with no judgment and no pressure. It's just you and a keyboard and a microphone putting your thoughts into video.