1837) I have always been interested in phrases and generally give them a little or a lot of thought depending on their context. When I hear, this too shall pass, I understand it to mean something similar to what Paul wrote in Colossians 3:2.
 
Paul said, think about the eternal things more than the temporary things. Why? Because everything on this planet is temporary except for our souls. In thinking about this, it makes sense to focus on what lasts, rather than getting bogged down in the temporary.

Yes, the things of this life will pass, so let’s invest in what eternal.