In the earlier days of my Japanese education, I would try to communicate in English via Japanese, if that makes any sense. I would have in mind something that I wanted to say, and translate it, as best I could, literally into Japanese. I remember I would sometimes tell my Japanese teachers 「いい週末を過ごしてください。」(Have a nice weekend) and as kind of a joke with my friends, I would call things ｢甘い｣ (sweet) when I thought they were cool.
The problem is, telling someone to have a nice weekend isn't really natural Japanese. No one says that. And calling something "sweet" in that way is nonsensical. There are all kinds of expressions, phrases, and vocabulary that just aren't used, and somewhere along the line you have to change your way of thinking. Granted, in the beginning your vocabulary and knowledge of grammar will be pretty limited, and it's definitely preferable to do your best to communicate even when you sound strange or unnatural. Eventually, though, you'll start to pick up the natural "feel" of the language.
I'm not exactly sure when I made that change, but it is recently that I've begun to consciously take note of and analyze some of the similarities and differences of key ideas and expressions in English and Japanese.
One that comes to mind right away is the use of the word "bad" versus 「悪い」（わるい). In English, we can employ "bad" in a wide variety of situations and circumstances. Some examples:
- This food is pretty bad.
- What a bad movie.
- I'm really bad at French.
- You invited him to the party? That was a bad move.
While there's more than one way to express these ideas, here's how I would say these things in Japanese:
None of my Japanese renderings use the word "bad" as we foreigners learn it in Japanese. Conversely, Japanese seems to use 「悪い」a lot more often when expressing the idea of fault. For example:
(Oh, our meeting was at 2? I see. Sorry about that.)
(No, it's not your fault. It's mine.)
In the first case, 「悪いな」 expresses that yes, the speaker was bad and he's admitting that as an apology. In the second, the speaker is expressing that whoever he is addressing isn't "bad." It's his fault. In Japanese, 「悪い」or ｢悪くない」are often used (along with せい) to talk about fault. The closest thing in English is the somewhat slangy expression "my bad."
There are tons more examples. If you're studying Japanese or another language and not yet at the point where you can break away from your native tongue in expressing your ideas, don't worry or rush it. It'll come with time. But being aware of the fact that you must change the way you think may help you get there quicker.