Choose Any Two
You may have seen the posters:
Three words are arranged in a triangle: Cheap, Fast, and Good. Below them is written a phrase: Choose Any Two.
As a rigorous rule, it’s not much use, but as a general model for the trade-offs you must make in a constructive process, it’s astoundingly useful, most especially because of its simplicity and brevity.
I think there are others. Most especially: Creation, Preservation, and Destruction.
I sometimes think that my two are Preservation and Destruction. I strive to preserve what is worthy of preservation, and destroy what is worthy of destruction. But despite countless tear-filled hours of trying, I cannot create worth a damn. I really don’t make anything of my own, and while I can sometimes do a great deal to improve the works of others, I cannot do as they do and create things myself.