You all told me - W5D3 with the 20 minute run is more of a mental block than a physical one, and you were right! I broke it down into 4 five minute increments, and the first two were tough, but once I got going, it wasn't bad at all. When I made it to 15 minutes, there was no stopping me!!
I was actually more concerned about my running partner - my dog Rosie. We've done the whole program together, and I wasn't sure she could do 20 minutes straight, but she did great too!
Thank you all for your encouragement - there's no stopping Rosie and I now!!