I was faced with the very real prospect of death a few years ago, for a short but horrible time. My feelings were really complicated and I don't think a trite phrase like the one in the OP really captures it. For me, the prospect that things might be entirely over once and for all pretty soon made me very honest with myself. It made me realise that a lot of what I had done in my life up to that point had been about living up to others' expectations and doing what I felt was "right" rather than what I actually wanted to do. The idea that I might die without doing what I truly wanted to do (because I'd assumed I had a lot more time) scared the living shit out of me. I realised I had been complicating things for myself totally unnecessarily by trying to be perfect. I'm not perfect, but who gives a shit? One day I'm going to be feeding bacteria in my grave, and that silly thing I said, or that money I lost, isn't going to mean anything. No one is going to care.
In a nutshell things became less important rather than more important. Stuff that once worried me now don't even figure on my radar, I just can't get worked up about it. Things will go wrong, and things will change. I might as well just enjoy what I can.
If you are pushing yourself through a job just for money, I think you will regret it on your death bed. Because you are easily replaced in a job, when you are not at all replaceable as a partner or mother and the idea that you've given more of yourself to someone who just doesn't care, while people who love you lost out, is extremely galling. However, I do think if you have a job that you get a true sense of satisfaction from, that isn't entirely about the money, you won't regret it, because the years are short but the days are long, and if you can spend your days doing something that makes you smile you are lucky, and it will improve your life.
Essentially I think what people will regret is not letting themselves be. Not leaving their poor selves alone to just have a good time. They'll regret poking at their harassed selves, telling them that they're not good enough, not doing enough. When you're dying you realise just how fab your much-maligned self was, and how little you valued him/her. That ugly, no-good person in the mirror suddenly becomes an angel who gave you access to wonders and you feel very sad you weren't kinder to him/her.
Be nice to yourself while you can, you won't be around forever.