I subscribe to /r/godlesswomen, if just to gain insight to a side of the atheist movement that I may (and, unfortunately, probably won't) see on /r/atheism. As a result, I came across this self post, in which a member of the subreddit posted about how accepting her eventual death made her realize how valuable the people are in her life.
I, myself, have come to the same conclusion: our time truly is limited. When I die, the electrical signals in my brain will fade and my brain will eventually decompose to such a state as to make the revival of me impossible (pending some kind of miracle technology, anyway). This is inevitable, unavoidable, and impending, no matter how much I may want for otherwise (point in fact, I had an epiphany as a teen that one of my biggest reasons for believing in religion was the comfort of the idea of life beyond corporeal death).
As a result of this, I find this to be a constant reminder and motivator to do things. For example, more than once, I find myself just feeling bummed and crappy. Now, I could stay in with my dogs (who I love to death - no pun intended), maybe have a drink, watch some TV, and call it a night (and, if I did this, maybe I'd eat through my book backlog at a faster pace). However, I mentally fast-forward to my deathbed (assuming I'm so lucky as to have the time to reflect on my life before I die): looking back, do I want to have missed time with people simply because I didn't feel like going out? Which is something I can enjoy more - the memory of a TV episode while on my couch, or the stories, jokes, and ideas exchanged with friends over drinks and food? The answer, of course, should be obvious.
Furthermore, it's affected how I deal with my personal relationships. When my theocratic uncle decided to unfriend me over a spat about the value of prayer versus a USO care package, I didn't pay it any real concern. Why not?
The short answer is: he's a bit of an asshole. The long answer is: I only have a limited amount of time before I cease to exist. This means my time and energy are bound by my eventual death. Yes, I could spend time and effort trying to heal the rift between us (though to what good, I cannot say - he and I are so ideologically opposed that we'd be at constant odds on issues of secularism, LGBT rights, and exclusion of Biblical science from schools), but that same time and effort that are bounded would be so much better-invested in helping a friend deal with family problems, or helping a friend with relationship troubles, or just spending time with a friend for socialization. When I look back on my life on my deathbed, would I rather have spent time working on a relationship with someone that I, quite honestly, probably couldn't tolerate their presence beyond discussion of the latest blockbuster movie, or spent time helping and developing friends who I trust intimately?
Acknowledgement of my death has also given me purpose in life. After I die, given enough time, eventually no one will remember me (I definitely don't have any kind of soul to linger around and remember myself). The only things that truly have a chance to survive me are my contributions to society, however small: promotion of LGBT equality, promotion of freedom of religion as well as freedom from religion, charitable donations in terms of time and money to help those in need, working to protect education from those who would seek to dumb down children in the interest of preservation of their religion, and other issues. Some call me loud-mouthed, obnoxious, and dramatic, but I simply call it trying to leave the world in a better shape than I found it.
All in all, life without death would still have meaning, but life with death leaves me with at least a sense of urgency to do shit.