It doesn't matter how much you think you have life sorted out, it just isn't that predictable. There are a million, million factors every day that we aren't in control of. Here is a quick video of the luckiest man in Russia yesterday, who was just quick enough when a bus's breaks failed. He didn't expect to die yesterday, but he nearly did.
I don't expect to die today, but I might. I don't want to live blind to that possibility. What happens then effects how I live today in every imaginable way.