- Overall, never assume an interview went well or badly.
You don’t have to outrun the bear, just all the other runners.
If the interview was tough, it could have been tough for everyone else who applied. And if your issues were emotional, you never know when you just might have struck some connection with the interviewer, like reminding them of themselves five years ago. Feelings work in strange ways.
- An interview is a two-way street.
Your email is unlikely to change their mind about your abilities.
However, the interview is also about checking if you like the company. Some candidates are passed over because the interviewer figures they didn't like the interview or the position enough.
If you express continued interest in the company/position in your feedback email, that's the part you can affect.
- Be brief and ask for feedback.
A simple "Thank you for the interview! I liked what I heard about the company and the role, despite my initial technical difficulties. I'd appreciate any feedback!" would be suitable.
This is part of general keeping communication down to what the other side doesn't already know.