Motivation

Why is it that thirty minutes of self-led yoga can seem like an eternity? Why can I put off cleaning my windows for months, literally months, but then when I'm 15 minutes into my yoga practice, I'm overcome with the need to CLEAN THOSE WINDOWS NOW.
Today was day five of my thirty day yoga challenge and when I weighed myself this morning I haven't lost an ounce. Not a single ounce. Suddenly my motivation to complete this challenge had evaporated. The thing is that yoga isn't (only) about weight for me. It is relaxing. My body feels better when I practice. I enjoy it. So why does five days of practice with no measurable weight loss begin the mental battle against this beneficial practice? I guess the answer is the same as always; I am a self saboteur of the highest order. So my challenge remains. I did my thirty minutes today and every day this week. It continues.