One is better than the other.
Instead of worrying about the time lost in a day, you can think and make the best use of the time that remains.
Thinking about the remaining time in life, in the same way, helps because we can’t recoup what is gone, but we can make the best use of what remains.
Instead of feeling bad about what you couldn’t do, you can feel good about what you did.
Instead of feeling bad about what you can’t do due to circumstances, etc., do what you can do.
Instead of counting what is not right, we can count our blessings and be grateful for them.
Instead of thinking about how competition ate your lunch, you can think about how they proved that a market existed for what you sell, thus reducing your risk.
Now tell me, is your glass half empty or half full?