You have just completed your interview. You did your best, and got across the 3-4 key messages you were hoping to convey. Everything went basically according to plan, but.. as you walk out of the building and begin the process of reflecting on your performance you start to have a lingering concern that maybe you didn't convey clearly the strong fit you feel between yourself and their organization.
The thought grows on you. Did you say the right things, or enough things? You start to wonder if the interviewer may feel you don't have strong fit with their organization. This causes you to reinvestigate your performance throughout the entire interview - maybe you also didn't demonstrate clearly enough the impact you had made on your current organization, or your passion for an extracurricular activity you are engaged in.
One natural reaction is to race home, turn on your computer, and then attempt to "rectify" all of these problems and concerns with one big email where you apologize deeply for your performance and then proceed to restate everything great about you, and what you "really wanted to say" during the interview.
This is a bad idea.
It is a bad idea because the interview is over, and no one gets second chances. It is a bad idea because the interviewer may wonder why you didn't communicate what you wanted to in the first place. Finally, it is a bad idea because your interpretation of your own performance may in fact be worse than the person who interviewed you! So that email can actually backfire and highlight bigger problems that may actually exist.
Of course, we have all heard that the thank you email is a good idea, and you should always send a thank you note to the interviewer once the interview is over. But if you cannot relive the interview in that email, then what should you do?
My advice for the post-interview thank you email? First of all, thank the interviewer for their time. In most cases, their schedule is busier than yours, so it is important to acknowledge your appreciation that they took the time out of their busy schedule to meet with you. Now - that could be enough, but if you are going to email them, it never hurts to add something - something which will allow them to remember you in a favorable way. This is your chance, not to relive the interview by clarifying what you wanted to say, but instead to reinforce one specific point about your candidacy. So, if you felt you did not clearly convey XYZ, then simply convey XYZ in the email. I hope when you consider my candidacy for your program/company, you'll think about how well my previous experience leading ABC would help me to contribute to your … Be specific and be direct, to ensure that your email is not too long. Don't attempt to apologize for your interview performance, or attempt to "restate" something you couldn't say before.