This day and that Day

“There are two days in my calendar: This day and that Day.”
― Martin Luther

Heard this in a sermon this morning. I can't find out where Martin Luther said it, so I will be a little suspect until I find the original. 
I think it means that "this day" is today. I'm not worried about yesterday or the future. 
I think "that Day" refers to the Judgement Day. 
Martin Luther was saying that I need to live today in light of how it will be viewed on Judgement Day.