And I thought it was rough contemplating the coming of forty! I very much like the inexorable "running from where I am, towards the end of my line" -- quite aside from the futility of trying to stop the passage of time (and the phenomena we all discover as we age, that the years become much shorter!), this reminds me of those dreams where you're running but you've no idea what from, and you know with absolute certainty that where you're running to is going to be no safer but you run on anyway. (Or maybe that's just me!)
I wonder, would you consider "I realize that I quickly/approach" as an alternative for L5/6?
I find the last three lines quite chilling. You have very aptly linked that contemplation of nothingness with blindness -- and "mind blindness" perfectly taps into that fear of forever losing consciousness. I almost wish I hadn't read this now
It could be worse