I am currently learning Korean and Vietnamese. 

For Vietnamese I try not to go to sleep until I feel I have learn a little more today than yesterday.  It isn't very helpful, but I always make sure that I am consistently taking lessons, doing consistent work from textbooks, reviewing vocab, and reading a novel (albiet, very slowly) in Vietnamese.  I find that having structure and a daily task list helps me.  So even if I feel like I had a bad study day, I at least made some progress.  

For me, learning new vocab, and understanding something in Vietnamese today that I could not understand yesterday is very addictive.  

Find something that you are really obsessed with and try to do everything that has to do with your object of obsession in Korean.

As an example, if you really like Super Junior, google every article on Super Junior in Korean and slowly get through all of them.  Look up every word you don't know and make note of the grammar that doesn't make sense to you yet.  Your desire to know more about Super Junior will motivate you do to all the tedious work.  You can look of up the lyrics of all the Super Junior songs, look up the words that you do not know, and try to translate them.

Unless you have an external force (like a significant other that only speaks Korean, or a need to speak Korean for work) I think you need some kind of obsession to keep you going.

Chức may mắn!