This gets into psychology, eh?

I suggest reading through alljapaneseallthetime.com/blog/

He has excellent tips. For example, to paraphrase, "just open up a lesson, don't aim to finish one, because that'll feel like too much work, and you won't find the time".

I have a language learning site, and we changed our suggested method to its users because of that better approach.

That comes down to communicating how to use your product to your users. I have to do more of that too.