Good design is to evaluate what you could do better, faster, different and more efficient.
Onur Cobanli explains:
In many industries, products become commodities, i.e. not differentiated from each other, therefore perfectly substitute-able, and therefore competing on price. Especially in such industries, but also in many others, small design improvements could lead to significant sales by making your design break the curse of commoditization; to make it different enough to have its own charm, to give the message to consumer and clients that the product indeed does not have a substitute. That's one thing. Secondly, in any industry, over a long period of time, repeating small design improvements, reiterations, and improvements will help you achieve a superior product that works better, functions better, that is loved by its users and desired by its buyers. In all cases, start small, small design improvements will always lead to significant sales.