"That is the way to learn the most, that when you are doing something with such enjoyment that you don't notice that the time passes."
Albert Einstein in a letter to his son
Some might call what Einstein is referring to here the 'flow' state, but I think it is more along the lines of simply being engaged. Being engaged and active in the thing that you are doing will lead to better learning outcomes.
I've written before about creating joy, but this quotation inspires me to harvest joy in my life. To seek and find those things that give me the sense of enjoyment so that I can learn more. I get a lot of pleasure out of learning new things, which creates interesting feedback loop of enjoyment, learning, more enjoyment, more learning etc.
Lastly, this quotation reminds me that, if I am not enjoying something, I am probably not learning much. Though there are things I must do and learn for various reasons, there had better be a good reason for me to learn something that is not enjoyable. Also, it inspires me to keep the balance of things I do tipped towards the enjoyable side because I don't want to miss out on chances to learn more.