We wake up in the morning assuming we'll be alive by the end of the day so delay doing those "less important things".
That list can get pretty long.
Telling important people we love them.
Eating the foods we know are best for our health.
Pursuing that role we really want because we're comfortable in our current job. Even though it's not quite it - just safe.
And so on...
Talk to someone who's beaten death. They know the truth.
We all are going to die. Sooner than we planned.
People don't plan on being hit by a bus, suffer a coronary, be in the wrong place at the wrong time or simply just stop living. They don't plan on not having enough time to do the things they keep putting off.
So the next time you think "I'm too tired, too busy, don't need to, etc." Tell your brain to shut up and just do it.
At the very least, whatever life you have left will be way more interesting.