Reply #37: Here's what I wrote back:

[SCRUBDASHRUB]

Dear XXX:

Thank you for interviewing me yesterday. I enjoyed meeting with you as well.

While I believe I would bring a lot of experience and make many positive
contributions to your firm, I have decided to withdraw myself from
consideration for the ______ position. It was after much
deliberation that I realized I am in need of a "standard" work schedule that
offers some flexibility.

Thank you again for taking the time to meet with me. I wish you the very
best in finding the right candidate to continue to grow your firm.

Best regards,
xxxx