“The best day of your life is the one on which you decide your life is your own. No apologies or excuses. No one to lean on, rely on, or blame. The gift is yours - it is an amazing journey - and you alone are responsible for the quality of it. This is the day your life really begins.”
It says "Viavraham zakeinba bayomim" - Avraham was old 'coming with days'. According to the Zohar Hakadosh this means that Avraham came to Hashem with EVERY day, he took advantage of every day. He didn't have time for newspapers, for television, for internet, for anything other than service of Hashem and never was a day wasted.
Once a day is wasted it will never return. Tomorrow has different possibilities, different potential and different "oros".
Tomorrow can never make up for today.