I accidentally found a great motivator. I am finishing my W5, and in the middle of this week a friend of mine asked if they could run with me. I said yes and decided to run a W1R1 with them so they wouldn't have a terrible time.
Well, I really hadn't realized my progress until I reran that W1R1. I couldn't get my heart rate to go above 150 since I am now recovering so much faster. Those tiny 1 minute jogs came so easy to me and I remember how hard they were just a mere 4 weeks ago. In fact, the friend that came with me was having such a hard time and it felt so nice to be able to tell them how I was in the same boat not too long ago.
So if you are feeling unmotivated or you are having a hard time seeing your progress, I recommend you rerun a W1 run. It'll make you feel so proud of yourself.