The most prominent and widespread explanation of the significance of the mezuzah is that it serves as a reminder. A reminder for what? In a widely-acclaimed 2013 TED Talk (Gratitude), David Steindl-Rast advised his audience to place post-its on faucets, light switches, food pantries, and other fixtures of a modern American home. Steindl-Rast procscried as a useful way for people to remember how fortunate they are to have running water, electricity, and all of the other conveniences that are afforded to us by modern life. Perhaps the mezuzah is also a kind of reminder to appreciate life and all of the opportunities that we have make the most of it.
Follow the link below to hear David Steindl-Rast's inspiring TED Talk.