You will probably have come across this question or some variant thereof.
Be it about your program, the exercise you do, the sets & reps scheme or just about the fact that you are a dedicated individual.
I found it very insightful what George Lee Mallory had to say about this stupid question (yes, there are stupid questions). Mallory died in 1924 near the summit of Mt. Everest and he may or may not have been the first person to reach the top of Everest, more than 30 years before Sir Edmund Hillary.
The first question which you will ask and which I must try to answer is this: What is the use of climbing Mt. Everest? And my answer must at once be, it is no use. There is not the slightest prospect of any gain whatsoever.
Oh, we may learn a little about the behavior of the human body at high altitudes, and possibly medical men may turn our observation to some account for the purposes of aviation, but otherwise nothing will come of it.
We shall not bring back a single bit of gold or silver, and not a gem, nor any coal or iron. We shall not find a single foot of earth that can be planted with crops to raise food. So it is no use.
If you cannot understand that there is something in man which responds to the challenge of this mountain and goes out to meet it, that the struggle is the struggle of life itself upward and forever upward, then you won’t see why we go.
What we get from this adventure is just sheer joy, and joy, after all, is the end of life. We don’t live to eat and make money. We eat and make money to be able to enjoy life. That is what life means, and that is what life is for.
In it he talks about the joy of scratching the surface of human potential.
He did a solo and unsupported crossing of the arctic ocean. From the north coast of Russia, through the North Pole to the north coast of Canada.
The talk (and the more detailed talk below) is well worth your time.
More detailed, 18min talk.