Sending the email in a clear state of mind ensures that the quality of the earlier writing is preserved. This will also allow you to catch errors you missed before you send it.
It doesn’t make sense to send the email when you are in a bad mood, so make sure that you feel good about what you are sending to the interviewer.
All that have been mentioned above are ways you can ensure that your post-interview experience goes well. However, there may be mistakes you didn’t notice, which may catch you unaware. You will be informed of the issues to avoid.