Instead of living everyday as if it was your last or as if it was going to go forever, how about living everyday as if you're going to die at around 80-85?
It really depends for people. You can keep track of all your thoughts and ideas meticulously, to ensure that none of them are a quantitative exaggeration or minimization of a linguistic translation of your present perceptions of the objective state of 'things'. But if you do that long enough, it is very hard to have an imagination, and you also can easily squash desire and fear this way as well. Dreams may also come out weird, and mathematical, logical, and computational terminology may seem to express multiple meanings about your conscious awareness (implicit metaphor - because logic + truth = ?, which gets very weird when you describe emotions or familial/friendly relations).
You can live assuming everything everyone tells you is correct, and you can assume this collectively forms your information sphere and consequently, your image of the world, and even then project that image onto something you call 'reality'. But it's a bubble. People change those bubbles because even though everything in reality tells them that they can not change the bubble, they know that it's still a bubble that you have to be convinced into in the first place.
The map is not the territory. -Alfred Korzybski