After all these years, I've identified a basic pattern to my ADD. It isn't universal. My lack of focus doesn't always follow this pattern, but I have identified this as one way my focus shifts.
For example, right now I am working on S&S for Alternity. I'm trying to keep real changes to the system to a minimum, limiting additions, and not adding any sort of mechanics unless unavoidably necessary. In short, I'm trying to keep it simple, which is true to the old school.
However, it is work. It does involve conceptualizing things, tweaking, twisting, and re-spinning certain aspects. Additionally, these modifications will need to be explained to anyone playing (which is a purely academic point), rather than just having us all play from the same book we all know. (We, in this case, being a complete hypothetical, of course.)
So, from all this angst will inevitably spring a desire to get back to something simpler and more pure. Typically, this leads me to S&W WhiteBox. I love that game. The elegant simplicity just sings. Then, I start actually thinking about doing something with it. It is at that point that I see all of its holes which I will need to patch.
Which brings me around to thinking that if I'm going to be doing all that work to make WB play S&S the way I want it to, I may as well be using Alternity as the foundation . . .