So you want to learn Japanese …
Playing is the best way to learn. Okay, maybe it is not the very best way, but it certainly ranks among the best. People who want to learn something should find an approach that they enjoy and, if possible, is even addictive to a certain degree. The way I learned some basics of the Japanese alfabets and characters, was through the RPG game Project LRNJ. I forgot most of it, since I have not practiced in years now, but I’m confident that I would pick it up pretty quickly if I were ever to start again.
I taught myself some Spanish and still actively try to maintain and improve that knowledge, applying the principle of enjoying the learning. That is by reading books, starting with translated works that I was confident to be interested in, and watching the Spanish news, movies and animated series dubbed in Spanish (Simpsons, Futurama, Family Guy) and eventually real Spanish programs, such as Los Serrano. Of course not everybody enjoys these things and it can be hard to get to the point, where you can actually enjoy it, so you do have to be persistent and have faith that your knowledge will improve to the level that you need to have fun with it.
So the next time you seriously want to learn something, you might want to try and actively seek a method that improves the chance that you will enjoy (part of) the learning process. Be creative with it!