I think one of the most important requirements to learning any language successfully is dedication. Without dedication, there can be no success. The best method doesn't work without dedication. That's really where the off-the-shelf language courses fail. Courses like Pimsleur probably do a great job until the course ends. After that, you can't really apply the Pimsleur method any more. And you certainly aren't finished learning. So you're left to your own devices trying to figure out what to do next. For experienced language learners, this isn't a problem. But I think the average language learner doesn't know what to do.
This means you need a plan. Sticking to a plan will at least get you somewhere and you'll know exactly when you will arrive there. I read a book in Japanese on how to achieve your dreams. The author has devised a goal-setting chart. You plan out every step of the way and therefor you always know what to do next. You don't get lost. Pretty simple, eh?
Of course, you need to be dedicated to your plan. The best plans won't carry themselves out. You have to carry out the plan. That is how you reach your goal.
So far, the only plan I have managed to see through, is the watching of 2,000 hours of Chinese. It seems I much prefer wasting my time and just relaxing. So how did I manage to complete the 2,000 hours? Well, I really set that as my one and only priority. Since I finished the plan, I'm now just like everybody else. I can't get in very much TV time, if any, in a month anymore.
I think too, that without a plan, you really don't have anything to dedicate yourself to. You can't just make statements like, "I'm going to be dedicated to my language learning." Such a statement is meaningless. What does it mean "to be dedicated to language learning?" What do you do in order to be dedicated? That's why you need the plan. With the well-thought-out plan, you know what to do. You stick to it and you execute the plan every day.
The more comprehensive of a plan you can make, the better it will be. Why? Language learning is multifaceted. You will be learning words, expressions, sentences, and for some people, grammar. You also will need to tune your ears to the language. Then you have output, speaking and writing. If you can devise a plan that will allow you to master the language, then you won't lose any time wondering what to do next.
It would be nice if there were some place on the internet where you could look at fully comprehensive language learning plans. Then you could choose the one you thought was the best. Eventually, people who chose and followed those plans would leave comments about how well they did once they finished the plan.
It's not easy. It's not simple. It does require dedication. Sometimes you might plan something that is too difficult for you. Your plan wears you out, makes you tired, creates burnout or fatigue. For instance, if you tried to learn 100 words a day. Then 2 weeks later you realize you need to review 1,000 words.
I'm trying to think of something to overcome the need for review. I'll let you know when I've come up with something tried and tested. Until then, think positive, be dedicated.