I also mourn the thousands of lives lost. It was a horrible tragedy.

I'm not sure that I agree with the day of mourning, although I certainly agree with the sentiment. Don't take this personally, it's not intended as such:

I'm not expert on the subject, but let's say that there are 300 million people in the US. Let's further say that at this point in time 1/2 of the population is gainfully employed. Let's suppose that the average person works 250 days a year for 45 years. That's 11,250 days in a person-career. Divide that into 150 million for the one day of mourning, and we end up giving the terrorists 13,000 more person-careers, along with it's negative effect on the economy. I'd rather work for the future.