Learning more than one language at once: it's just a matter of time

The question is always the same: is it possible to learn several languages at the same time?

My answer is: absolutely yes. The brain works like muscles, and the more you practice it in a skill, the more it will be able to excel in that specific function.

And I don't even think that you have to choose very different languages (for example, Arabic and French), as the more the languages you've chosen ​​are similar, the less mnemonic effort will be required.

So what is the real obstacle? Lack of time!

My native language is Italian, I learned English, French and Chinese as foreign languages. Now I want to learn Japanese and I've realized that the only obstacle I have to face is the lack of time: since I have quite a busy life, I either give up the plan of improving my skills in other languages ​​(in particular Chinese and French), or give up the plan of studying Japanese.

However, "to give up" is absolutely an unpleasant decision to make, and then I have no other solution than to optimize the time available.

I will spend most of my time studying Chinese and French, in these languages ​​I have to face the transition from the intermediate to the advanced level, it is the most difficult and most demanding leap and it will require all my energy. To make better use of my time, only language textbooks will be on my desk: no TV shows, no songs or other authentic materials available on the Internet. Research should be done to find the right materials, keep a diary of my progress, look for new structures in grammar books and check that the number of new words is suitable for my level. Simply put: to the time spent studying, I would have to add extra time to look for "study materials", and as I've just said I have no time.

As for Japanese, I will spend only one day a week studying "Japanese for today - Gakken", so that I should finish the book in about six months. It's a long time, I could finish it in three months, but it's the only way to learn Japanese while I'm trying to improve Chinese and French. 

And this is the other major obstacle to learning more the one language ​​at the same time: not wanting to accept that more time is required to achieve our goals. Yet sometimes you can achieve more simply by waiting and being patient. After all, what sense would it make to quickly finish Japanese for today and not to progress at all in French and Chinese?