I once had a teaching assistant who would look at me and say: "If only you applied yourself, you could do some amazing things."
When she'd say that to me I'd usually do one of three things. I'd deflect with a joke, protest but I do apply myself, or simply shrug and say nothing.
Looking back, the TA was right. I wasn't applying myself. It was a 17th Century Literature course, I was required and didn't choose to take the course, and my GPA was a solid 3.8. So what did I care? I hit academic cruise control and relaxed for the entire class—because real application wasn't needed for me to get a good grade in the course.
Looking back, I should've applied myself. But when you're a second year undergrad, you don't really think much about anything other than yourself and your comfort, and that pretty much forces you into an apathetic state. Out of all the responses I had for my TA, it definitely was the shrug that was the worst. It represented my willingness to admit I wasn't working hard, and not feeling the least bit ashamed about it.
Back then, the iPhone wasn't invented yet, which means application didn't primarily mean something on your phone or computer. It simply meant "the practical, invested, and intentional doing or expression of something."
Now we have fancy apps that take care of that work for us.
But the best app? Our own application. Our willingness to apply ourselves to what we do.
And the worst app? Our own apathy. Our willingness to under-apply ourselves to what we do.