The title says it all. There's nothing more to it. Nothing is amazing in the same way as this realization is.
Today is the best day of your life.
You might have memories of excellent days in the past, and you might even think that those days were better than today. But on that excellent day, you had so much less than you have now: all the other excellent days that came after that, and the ability to reminisce about them.
Today, you're wiser, more experienced, more talented, skilled, and refined than on any other day in the past. You've read more books than any other past version of yourself. You've had more life-altering experiences than any other past version of yourself.
All you need now is to make today count. Do something exquisite. Work, enjoy life, get a new experience, read a page from a new book, reread a book you've read in the past when you understood the content differently.
And if you want to take this paradigm to the next level, make today unique in as many ways as you can, so that you'll remember today in the future as one of those excellent days.
What could make today both count, and unique?
For me, I'm thinking... get a rush from working effectively. Then, with that rush of feeling good, I can ride the rest of the day while getting my sister a birthday gift, drinking an exquisite cup of americano, taking a little road trip while listening to the best of old Nickelback, walking around town and enjoying the sea breeze, come back to the office to get another small rush of productivity, and finally, go home to get a cold shower and then go lie down on a yoga mat midst the balcony jungle in the evening, basking in the knowledge that tomorrow will be another great adventure.
I don't know if it could get any better than this. (Although I admit that my mini vacation was insanely awesome as well.)
To the best day of your life!