I am reasonably fluent with English and can express arbitrary thoughts by using it. However, when speaking fast, I often use the wrong pronoun (from "he" or "she"). I am also aware of "they", which I have not misused thus far.
I have no problem understanding the difference between "he" and "she". I do not make the mistake when I have time, or when I write. The probable reason for the problem is that Finnish, my native language, has only one gender-neutral word "hän", not separate words for males and females.
How do I learn to not make this mistake anymore?