Be sure that your clips are set loosely so that it is easier to unclip. Once, I had that squared away with my newest bike the falls disappeared. After that, it is just practice. I am 46 and I ride with a few men who are close to 70. We have all fallen at one time or another. (I have fallen a grand total of 7 times - 3 with my first bike, 4 with my current bike). Fortunately, I have always fallen when I was almost completely stopped. I forgot to unclip or leaned to the wrong side. The good news is that none of us have suffered a serious injury from those falls. A few scrapes from contact with the asphalt and bruises. Just remember that it is usually when you are tired or distracted that you will forget to unclip. It was all I thought about at first, but now it is a natural reaction. Good luck!
"Nothing compares to the simple pleasure of a bike ride"~John F. Kennedy