Of course, we may not even have tomorrow. How many lives have been lost through disease or accident even at very young ages? God may require your life at any moment.
So why isn't everyone living each day to its fullest as if it might be their last? Why, even if we think we shall live a normal life into old age, we still don't see just how fast that time is passed and therefore, we don't make the most of our time daily?
Well, the simple answer and the correct answer, is sin. This can manifest itself in many ways, even as simple unbelief as we try to hold on to the world in one form or another, but no matter how it manifest, it is a picture of the flesh and its desire to do what it wants, when it wants, and how it wants, here, now, and forever more.
I'm not going to lecture as to what you should do or not do with this bit of information that I am sure you yourself (especially as a believer) have probably thought about many times on your own, but simply to just lay it out and let it be a reminder. As we already almost end the 1st month of the new year, let it sink in, just how fast even that time has flown. Then, ask yourself if your priorities, thoughts, actions, and anything else you can imagine are being taken captive by Christ or by a world, which will pass quickly for all of us in some since or another, only to have us wake into a better world, which shall never pass, or sadly, wake to damnation because we forsook the truth for the lie.