How to motivate language learners

I often say that English or/and Japanese is/are difficult. According to one of my students, though, I shouldn't say such a thing. She told me that I should say you-can-do-it things all the time, otherwise she would feel that learning a language is really really really difficult.

Let me excuse a little bit. When I said that English or/and Japanese is/are difficult, I am not trying to scare my students, I am trying not to boast about myself as somebody who can speak both language to some extent. Well, this explanaiton didn't satisfy her.

Anyway, people can boost their abilities or skills according to enviroment, so motivating students are important.