Onur Cobanli explains:
So what is intelligence and what is diligence. Intelligence is your capacity to understand and to think good. To think good, understanding alone is not enough; you need to have the proper wisdom, you need wisdom to be able to come up with the right mental connections and to form correct ideas. Diligence is your perseverance and capacity for carrying out an action; your ability to get bored, to put in the effort, your vigour. To put in other words, being solely Intelligent is like a computer having a fast processor, but Intelligence is meaningless without the software; the software which runs on your processor is your wisdom; your wisdom encompasses all the experiences, and knowledge and the overall method in which the information are processed. Diligence is your energy; diligence is your cost; diligence is the amount of time and energy you can allocate for the process. You need all the intelligence, the wisdom and the diligence, to come up with a good idea that matters. This is the abstract. In the most basic level, diligence for good design is research and iteration, and intelligence for good design is your creativity and inspiration; so good design requires creativity and iteration.