It takes a long time to build a wall. Today, a lot of people or businesses try something new for a few days, weeks, months, and after failing to see instant results, decide to pull the plug. There's only two reasons for this: either the person made a mistake, or they weren't patient enough (most of the time, it's the later).
Virtually everything today happens at near instant speed. Instant rice, instant abs, the "90-minute MBA". It took Michelangelo four years to complete the Sistine Chapel. There was no book called, The Four-Hour Fresco. There's so much potential value to be created from investing in and leveraging time.
When a bricklayer works as hard as he possibly can for one day, he could easily reason, "I haven't finished the wall, time to start something else". Then the next day, he does something else and gives up on that too. The actor Will Smith tells an amusing childhood story about he and his brother building a wall for his father. It took them a year-and-a-half.
There's a strange, eloquent beauty in persistence, almost defiant. Nobody knows why Forrest Gump keeps running. Even Forrest doesn't know, but in time, he's able to inspire an entire movement and gain hundreds of loyal followers. When's the last time you started a project that you knew would take a really long time to complete? Did you give up? Time is one of your most valuable resources, because it's in time that the seemingly impossible becomes possible.