Speaking in other languages in a tiring thing

It's been a very long that time I didn't write anything here, but it doesn't mean that I quit learning languages or suspend it. I am still working on it and starting learning Korean now. My learning partner of this semester is from the Philippines and she came to Taiwan without knowing any Chinese. So we have to speak in English of course. Things were okay at first, but recently I got tired of speaking in English. I asked a Japanese exchange student who's been in Taiwan for almost one year, she agreed with me that speaking other languages instead of your mother tongue is really a tiring thing. Because when we speak in our mother tongue, we just speak it out spontaneously without any thinking. But when we speak in other languages, we think too much. I think it's much more efficient to learn a language in the enviroment where the language is spoken. Because I am in Taiwan, sometimes I even speak to my leaning partner in Chinese and I am not aware of it at all. It's hard to switch the languages fast.