When it say “critical inch” it means that you give an extra effort on your extra time that can make a difference. This critical inch may aid to the growth of a business or project.
One example is saving money, everybody can put $5 on their piggy bank every pay day but only few actually do it. At the end of the year you can feel the difference. You have some money in the future when you need it.
Another example is to prepare for school or work for tomorrow. It’s better to prepare everything before you sleep so that even if you wake merely on time you’re ready to go.
When you are on a coffee break; you can think of productive idea that you can use for your everyday life. Others are just having their coffee for socializing while you can do both.
Those examples are using some extra effort and time that can help you prepared.