Mimi - the first time I fell w/ clipless, I could not stop laughing! Imagine, there I was on the ground, still clipped in both sides and no way in the world I was going to get UN-clipped in that position. Had to get one of my friends to lift the bike a little so I could pedal and get my feet into position to unclip. I still laugh when I think about it. I suppose I could have taken off my shoes and disengaged that way had I been alone, but it worked out. Sure I got a bruise or too, but remember falls at 0mph don't have near the impact as say a 20mph crash. You will fall. You will survive. It's just a rite of passage. Oh, yeah, and I was 54 when that happened.

In the meantime, go out in your neighborhood, and practice stopping at every intersection and unclipping and actually stopping, putting one foot on the ground, and starting again. A few trips around the block like that will really help. Anticipate stops and slow-downs. Esp when riding with a group, don't follow too close, and always be ready to unclip your "unclipping" foot when traveling slowly. Approaching intersections I always unclip one side just in case some traffic of any sort materializes. It will soon be second nature and you'll never go back. Good luck!
Martha