Yesterday, Today And Tomorrow

Please correct with my grammar mistakes:)
-----------------------------------------------------------------------------------------------
Life is short, sweet and precious. God only gives us a limited amount of time because he wants us to make the best use of it.
Our lives are made up by thousands of yesterdays, todays and tomorrows. Samuel Ulman wrote: "Youth is not a time in life, it is a state of mind". Indeed, the quality of our life is not measured by its quantity. People moan over the passing of days, but few of us spare even a minute to think how to make our lives more meaningful. No matter how we spend our days, they will be gone anyway. Instead, we should pay more attention to the present - today. It is not an abstract concept, but something that we experience every day. Live your life like there is no tomorrow! Seize every opportunity, you will be challenged, inspired and motivated. Your life will have new meanings. Even if it doesn't, tomorrow will bring new chances to fulfill your dreams. But never, ever think there are countless tomorrows. Appreciate every day, be thankful. Yesterday is history, tomorrow is a mystery, today is a gift. Live up, try new things. Make every day count. :)