Language learning tendency. Flaws.

We can only take part in things you could already understand

The hardest part about learning a language is creating a space in your head, almost as if you're creating another mind (within the single head of yours that you have). So that your thinking can be done in the language you're learning.

After you master learning like that, is then, when translation should come in. I think many of us starts off learning a language as if everything is translatable. I mean we know that its not, but somewhere in the language learning process we neglect/forget that knowledge and do it anyway. We think of words with equivalent meaning in the language we speak in, and unconsciously use that as our basis for understanding that word (probably until we come in greater contact with interacting with speakers of the language your learning). You can probably see the flaw here.
We can only learn, what we already know. That is, we learn about words that already exist in our language. The thing with language is that words can exist with a whole new meaning in another language. 
So essentially, we're learning through mindless assimilation. Think about it, if we take a word from another language and think of it in term of our own language - what kind of knowledge base are we building on? The one that is in our language. This isn't what you want if you aim to know another language well. You will eventually want to be able to think in that language you're learning to communicate efficiently. As to, referring back to your native mind then re-enter your self learnt language mind to conceptualise things.
['Assimilation' is one of those theories that cognitive psychology will cover when you learn about how your brain learn new things.]

So how are we suppose to learn if we don't assimilate it to things we already know - i.e. how are we suppose to learn a language if we don't use the language we know already?

How is it possible going back into a blank state, so we can create a mind of its own?
Easy. At the same time, not so easy.
I'm sure many successful language learner have said this in their own way, but in scientific (which i think is straightforward) terminology it's called learning through modelling.
This mean, we observe from a model (a Korean person, kdrama etc) and we simply copy from them. Think of it as a baby developing skills, through mimicking everything possible. This way, we copy well and have the potential to think, behave and perform like a native speaker would. Even if it seems a little mindless at first.

When your language skills in the foreign language becomes more developed, that's when we should be looking at equivalent word in the respective languages that we know.