Surely at one point in your life, someone would have told you to live your life like there's no tomorrow. You got to enjoy the things you have and live in the moment. Do what you want right now because you might never get a chance later. On the other hand, don't you feel it's sad to assume that tomorrow may never come? There are goals and tasks that takes longer than a day to complete. We all need something to look forward to. After all, hope is one the strongest drive you can have in life.
I think we should do our best today to have a better tomorrow. We should push ourselves to the limit every single day not because you might not get another chance but to shape a happier and better tomorrow.