I think 愉快學習 = the way that you could learn effectively and happily.
I would like to cite an example of what is 愉快學習 in LOGOS.
中文科課程設計 is very good.
They have 溫故知新 after each chapter, it's simply a quiz. But it's not something like boring 中文默書. Remember that when I was young, the traditional school ask us to have 中文默書. Even I got full marks but I didn't know how to use those words in my essay. I still find some schools have 中文默書 nowadays. My son will not like this kind of boring thing, instead he accept the teaching in LOGOS and get much benefit and success from here.
Also, one of his interesting homework last week. The main theme is to teach them to write 便條. The content is very funny and let my son happily complete it in few minutes and did very well.
Thanks LOGOS's teacher to work very hard to design the curriculum.