What is the biggest mistake you ever made and "vowed" never to repeat?

What is the biggest mistake you ever made and "vowed" never to repeat?

I have thought about this question a lot. I have made mistakes in weddings I know, but they have been small ones, mostly typos.  I guess the biggest mistake was misspelling the bride's name on a complimentary bound copy of the ceremony that I provide the wedding couple.  I knew the correct spelling and made a typo when I was preparing it. 

I apologized to the couple and prepared a new copy with the correct spelling.  I have taken steps to not repeat the mistake.

This would be the shortest blog entry in my history if I stop now so I will relate a story about a mistake I was witness to.

I was doing a wedding at Bee Tree Park at the mansion gardens. I had done the rehearsal on Thursday and was showing up an hour early, as is my custom, on Saturday to set up for the wedding. I was surprised because there were some guests already sitting in the chairs that had been set up for the wedding. One of the items I was carting in was a music stand.

One of ladies there saw the music stand and came over to me and said, " I sure could use that, I left mine at home. Could I borrow it?"

I explained that I needed it.  She asked "Are you playing music at the wedding?" "No, I told her. I am the minister." "No, " she stated, "that can't be....I am the minister."  " Well I did the rehearsal on Thursday," I told her. " And nobody has called to tell me I'm no longer doing it.  Let me ask you, what is the name of the Bride and Groom?"

She and the guests in the chairs were at the wrong wedding. The wedding she wanted was at the other end of the park.  And it was already ten minutes after the wedding she was doing was supposed to start.

I learned a valuable lesson. Whenever I do a wedding in a park I always pin down exactly where the ceremony is to be held.