Your eyes have seen my unformed substance;
And in Your book were all written
The days that were ordained for me,
When as yet there was not one of them (Psalm 139:16 NASB).
For an older fellow, I am reasonably healthy. I am not much to look at and, believe me, no one confuses me for Brad Pitt or George Clooney, but I have only taken seven sick days in the last eight years. Last year, a relatively minor condition necessitated an appointment with a doctor. This was my first visit to a physician's office in fourteen years. I have what is known as "white coat syndrome." Doctors make me nervous. Nervous? Did I say nervous? What an understatement--I would just as soon face the hangman.
Anyway, my situation was treated and all seemed okay. But when I returned for a six month follow-up, a no-nonsense nurse informed me that I had gained nearly twenty pounds and my blood pressure had risen. How could I justify gaining all that extra weight in only six months? And that extra weight may have contributed to the higher blood pressure reading.
Frankly, I do not want to be tethered to a pharmacist for the rest of my life. Some people are content to swallow pills as a means of propping up their faltering health, but I would rather make a lifestyle change in hopes of reducing my dependency on medicine.
I have thirty days to drop some weight and, hopefully, my elevated blood pressure. In a month, I am to report back to my physician and, when I do, I want him to say, "Good job! You've lost twelve pounds and your blood pressure is looking better, too. Keep it up!"
So what does all this have to do with your question? You and I experience time sequentially. We live second by second, minute by minute, hour by hour, day by day, and year by year. To illustrate one's life, we could mark a point when the individual was born and another point when that person died. The line between birth and death would, indeed, represent our subject's life span. Are you with me so far? Good. You might even say that we experience time in a linear fashion.
God does not experience time in the same linear fashion. God exists outside of time. He is not subject to the confines of time. He lives beyond time. He is not a slave to time. For that matter, God created time and time is His creation just as stars and planets and people are His creation. Time is subject to God. God is not subject to time.
As such, God knows the future. God is never taken by surprise by some unforeseen event. Nothing catches God off guard. God never, ever wonders what is to happen next.
Yes, God knows that day that I will die and He knows the day you will die. Considering all that I hope to accomplish before I go to see the Lord Jesus, I hope my day is well into the future but, yes, God knows the day we will die.
But I have a say in this, too. Which is why I am eating less and exercising more. And this is why I wear my seat belt, operate my motorcar at reasonable speeds, and lock my door at night. This is why I don't play Russian Roulette or use electrical appliances while standing in water. This is why I am not going to have an extra large thin crust pizza for dinner, though a thin crust pizza piled high with toppings sounds terribly good right now.
If the days of my life were fixed by God and nothing I did would shorten or lengthen my days, I would have never stopped smoking back on March 1, 2001.
If I stopped here, I would have only partially answered your question. Stay with me a bit longer.
A few months ago, my daughter had a miscarriage. My precious little grandchild, still forming in my daughter's womb, died before birth. My daughter and her husband were broken-hearted. My heart was broken, too. Though I had never seen that little unborn baby, I loved that child very, very much. And one day, I expect to see my first grandchild in Heaven. Why did my grandchild die before birth? I don't know. And, unlike me, that sweet little unborn baby had no say or control over its own health and well-being. My daughter was properly caring for herself. In this case, we might say God had fixed my grandchild's days. Maybe.
I believe, too, that God will keep someone alive until that person's purpose has been accomplished. Let us recall the life of the Apostle Paul. He had been arrested, beaten, shipwrecked, stoned, flogged, starved, viciously attacked, bitten by a venomous snake, and chained to Roman guards throughout his ministry. My friend, God was in the business of keeping Paul alive until the work He had set before him had been accomplished.
After running the race and crossing the finish line, Caesar Nero had the Apostle Paul beheaded. But until Paul had finished his work, God made certain that no enemy would take his life.
These are deep waters, my friend, and such mysteries are beyond our comprehension, but, again, God is sovereign, He knows the future, and you and I have certain duties, responsibilities, and decisions that will determine the outcome of our lives.