How funny. That was the workout I was theoretically doing this morning, too! I made it through 4 of them...humidity does bad things to my heart rate.
I admire your independent motivation - I only did it under peer group (except that they are less than half my age) pressure!
My self motivation is not what it used to be. If I set myself something like 5x1km out of the blue, I have a tendency to get through two or three then tell myself I really don't have to be doing this and give up.
If on the other hand I have a pre-prepared training plan, there's usually no stopping me. Haven't had one of those for a fair while though.