I find it useful to think of it as forces pulling on the design, similar to physical forces acting on an object. There are forces that try to keep individual truths/knowledge and responsibilities in a singular place, there are forces that try to minimize abstractions, coupling, dependencies, and indirections, there are forces that try to maximize coherence and separation of concerns, and so on. It’s an essential part of the job of a software engineer to balance those adequately in the design of the software.
Right. There are also "forces" like management who want the project to be finished yesterday.
Another metaphor I like for programming is Chess. Any line you add to the program constrains its future development, becomes "weight" or "force" that pulls your development into some direction. Sometimes you have to sacrifice features like pawns. Sometimes you may sacrifice security, you may think it is secure enough. The outcome of this game is often a draw, or stalemate. And the same game can continue for years.
