As a coach, I get the benefit of learning from the experiences of others. One experience for which I am particularly thankful is coaching older men, particularly CEO's and others who have been professionally successful.
What I tend to see is that towards the end of our life we tend to change priorities. Men who missed much of their own children's lives to be at work will try to be very involved grandfathers because they feel they missed out. They also speak about valuing other things - like time with family, a nice sunset or a good movie tend to make them happier at this stage too. They value little things over the push to 'get ahead'. I think this is a good indicator of the things that are actually important with some perspective.
As a man and a dad, there is often (mostly) unspoken social pressure to be the 'provider', and I find this mindset very helpful to remind me of what's important.
I'm not saying ignore your long-term goals for the here-and-now, but one thing the "live like your dying" mindset can bring is a sense of healthy priority and satisfaction to your day. It also takes the stress out of some of your decisions.
The attached video was a confronting ad asking the terminally ill about their priorities. It was made by UBank for exactly this purpose. They received plenty of flack over it, but in my experience it's not technically wrong - this seems to be how people realign their priorities when facing their mortality.
One way you can grab this mindset today: When you have to make a tough decision about how to spend your time or money - think "When I look back in 20 years, what will I be happier that I did?"