live as if it was your last day?

So there is a lot of teaching out there focuses on meditating on death. A lot of it talks about living life as if it was your last day, week, month... in that this way, you don't take life for granted and it wakes you up instead of just passing time... These same teachings talk about how life should be lived in reality and not in your mind. My question is... isn't "pretending" it is your last "day", "week", "month"... itself a construction of the mind? Doesn't that distort reality? Is that really the "correct" thing to be practicing?