Work smart means you are not only use your strength but you also need your brain to think what you can do to have more. That will make you more creative to search for a new idea that can bring you more chances to get what you want. Not many people realize this and still use their strength to work while they forget that they can use their brain to search for opportunity to achieve their goals.
Work smart will open more ways to see the chance to do something. He can delegate the work and do other things that help him achieve the target.
I think the word strength seems strong and might fit more better in the ' working hard ' category. When it comes to working smart, it is known that we are using minimal efforts here. We can as well say that brain is more needed in working smart but yeah, that workers here are good thinkers. Once they do one project, they might think of another and so on... again.
We can do more other work because working smartly saves us time or it allows us to work passively. Sadly yeah that not many people realized it. I think this is also because they just work and work and doesn't pause sometimes to realize some things, or they simply have a weak mind. Anyways, as long as they work fairly, I think that is also okay.