I applied three times, and received my first real acceptance this year after being shut out in previous years. Obviously it depends on the individual and what other interests and opportunities one may have. I simply couldn't (and can't) envision another career path for myself. I, also, am somewhat of an insane optimist so it was pretty easy to "bounce back" quickly after being rejected across the board twice. If I had been shut out again, I probably would have applied again this year. Meanwhile, I realized this time around that, despite my acceptance (only one, so far – either way, I am grateful), my application could have been clearer, better, more strongly situated in the current realm of academia. I could have contacted professors ahead of time (which I did not do). I could have improved my GRE scores. I could have submitted a better writing sample. So, essentially – I do think this process is a crap shoot. I could have been better. I'm certain that my application kept improving over the years, but, I could have easily been shut out again this year. But, regardless, I kept applying. I can't speak to anyone else's goals or life circumstances or whatever. But for me – it was worth it.
Anyway, I'm rooting for all of you. This is not meant to be "inspiration," per say – it's just my reality.