Sandstone,
I stand by what I said above: self-undoing tendencies can manifest anywhere in a natal chart, and that’s pretty self-explanatory.
The Sun and Saturn should not be taken to represent strength and weakness, as dignity and debility determine strength and weakness. The Sun represents the native and Saturn represents discipline and restriction, or even wisdom in certain instances.
If you view the twelfth house as the final house in the social hemisphere and you also consider it to be weak, then you must also view the culmination of everything acquired throughout the preceding five houses to be weak. Why does completion have to imply that something is weakened? One could certainly view the twelfth as a graduation or an attainment, and in that sense it makes no sense to consider it weak.
A graduation or culmination would actually (in my mind's eye) point towards something weakening in strength. You are done, you have nothing left to do in regards to it, thus it doesn't take up a ton of mental space ( 12th subconscious).
I also disagree that Saturn and the Sun should not be viewed in terms of strength and weakness without looking at dignity. It's about breaking the planet down to its fundamental and essential nature.
The sun is strength. It is the reason we are even here. It is life force and what could be stronger than a force that creates all that you see?
Saturn is weakness because it shows where we ourselves are weak. It shows the place where we need the most work. With time we can strengthen the area that Saturn rules or governs, but at its fundamental level, Saturn represents our weaknesses.
Just my opinion. I know it sounds very much like I see no room for another view, but that's just how it came out and I am too lazy at the moment to retype.