Dear Felix
It was a pleasure to meet with you the other day. I was anxious to learn more about your firm and its plans for the future.
Unfortunately, I do not feel my qualifications suit the [STATE POSITION, ex. sales manager] position at your form. [STATE REASON, ex. As you know, I prefer to stay close to home and will not be able to travel as extensively as the position requires.]
Nonetheless, I truly appreciate the opportunity to have met with you and I sincerely wish yourself and your firm the best in the future.
Regards
Lydia