Time is a finicky thing. Our perception of time and how fast, or how slow it passes seems to often be linked to what we're doing at that specific moment. I think I can safely assume that most people are intimately familiar with periods in their lives where they've been subjected to experiences so painfully boring that a minute feels like an hour. On the flip side, when you're able to get yourself into a state of flow doing work or an activity that fully engrosses you, you can completely lose track of time; Hours can pass unnoticed when you're in a flow state.
How we think about time can also be highly dependent on how old we are and our life experiences. I myself can think back to when I was only a few years old and barely considered time. When we're very young it often feels as though we have all the time in the World and that it's going to take forever for us to get bigger and older. But, as we age, we learn more through experience; we slowly begin to realize that time, at least for us, is finite. Taking a positive view of the fleeting nature of time can be a motivating factor to live life in a more meaningful manner. Time, although unable to be contained or have more created, is ever present, and our perception and respect for it is everything.
As a side note: if you decide to start tumbling down the rabbit hole of quantum mechanics, theoretical physics, black holes, etcetera; you'll find yourself with many more questions than you began with. In the end, I believe that we should avoid taking for granted the time we have and learn to appreciate each moment.