James Kovac seems to have a gift for explaining stuff. I though his Loosen Up article on MSDN was brilliant.

When talking about creating loosely coupled designs, he says:

The intent here is not to build an infinitely extensible but hugely complex and unusable generic framework. It is about reversibility. How easily can you change your mind with respect to design decisions? Do you have an application architecture that responds well to change?

This really hit home. I like to change my mind a lot even during a single hour of coding. I find that keeping concerns decoupled and cohesive is very useful for allowing rapid change. It also takes practice IMHO, and requires a lot of thought about the domain to find the correct seams.

He also talks about Inversion of Control, testing against mocks vs the database, and much more. A great read.