I don't actually know Japanese, so here are my two cents for what they are worth:
I hear that languages are often classed in 'families', and English and many other European languages are very similar since they are derived from the Latin family? It's easy to draw comparisons between French and English, or French and Spanish, or Spanish and Italian.
So it's important to realize that Japanese doesn't come from the same family and to not expect there to be similarities. I think if you believe that you will be learning from scratch completely -- and not expect there to be anything that will make it easier for you -- you are less likely to have false expectations and thus be disappointed.
I'm not sure if Chinese and Japanese are from the same family of languages. Some Chinese characters are used in Japanese, though the meaning can apparently differ occasionally. Anyway, when I am thinking in Chinese, I'm not thinking in the same way as I do for English and French. I can understand French in terms of English, but I find it much harder to understand Chinese in terms of English.
That is why I feel it's important to try and learn within the language itself as much as you can, to not keep thinking 'what is it in English?' but to derive meanings from context as much as possible. Perhaps you can treat it like learning a language from scratch as a baby would, without the support of previous knowledge to guide you. Words can only be translated so far before they lose a lot of meaning.
Watching a lot of anime is apparently very good for learning Japanese as well. (There's a phrase in Chinese which goes listen-speak-read-write, and essentially shows the pattern of successful learning. You've got to understand what is being said before you can speak, and speak before you can read, and read before you write.)
Anyway, good luck!
