Sending out the wrong email

I regularly send out a newsletter to 80 people. I use a program on my computer which automatically sends the emails, using a list of recipients and the file that I send. However today I discovered that I had sent the previous edition of the newsletter. Oh no! I think that from now on I wlll always test the process before processing all the emails!
I found out the cause of the problem. I had saved the file in the wrong place in my computer. I knew there was something unusual happening, yet did not check that the system was working. I have learned the importance of being aware of those times when I notice something unusual, and stopping to consider if I need to do something about it.