All things, my Lucilius, are another's matter; our time alone is our own affair. Nature sent us into this one fleeting and slippery possession, from which anybody who wants to can cast us out.
Time is our own in the sense that we can choose to make proper use of it. Seneca argues frequently that life is not short, that it only seems so because we willingly waste time, and that a virtuous life can be lived just as well in a single day as in an hundred years.
Another man's use of his own time - even if he chooses to spend it viciously, even seeking my hurt without cause - is his own business, not mine. Likewise, just about anything else - from the length of my life to the rising and setting of the sun to the rush hour traffic to the weather - are alien to me. How I use the time I have been allotted by Nature is my own affair. Not even the desperate junkie who puts a knife to my throat cannot rob me of my use of time - he cannot force me to spend my last seconds of my life as a coward.
Seneca, though, reminds us that Nature has given us a fleeting and slippery possession. That desperate junkie willing to kill for the possible pocket change I have on my person can indeed shorten my time suddenly, as can myriad other factors beyond my control. I had better, then, start living life well now, not later. I am not promised tomorrow, or even the next second. [See also next post]