Maybe I should correct that to "No useful or valuable thing can be learned in a day."
The good stuff, the stuff that will make you stand out from the pack, the stuff that will make you special is the stuff that requires practice. Practice is the key.
Very, very few of us can become elite by just relying on our natural skills. (i.e. Allen Iverson's famous "Practice" rant–he was elite!)
By gutting it out, by making time for it, by practicing every day, you will become very good. Practice a task for 100 days and you'd be surprised at how good you can be.
What may surprise you, even more, is that almost nobody is willing to dedicate themselves for 100 days to practice anything.
100 days of running.
100 days of working out.
100 days of shooting a portrait.
100 days of reading.
100 days of drawing.
100 days of eating healthy.
100 days of meditating.
100 days of writing something.
100 days of making a piece of artwork.
100 days of going to sleep at the same time (and waking up at the same time!)
100 days of cooking a meal.
100 days of practicing a sport.
100 days of PRACTICE, PRACTICE, PRACTICE.
Of course, more than 100 days is even better, but 100 is a good start. You will be great at whatever you stick with for that long. But almost nobody ever sticks with it and most of us live our lives that way.
Think about how much better you could be at almost everything you do in your life if you set aside time to practice.