"…say little and do much, and receive every person with a pleasant countenance" refers to the attribute of humbleness. One should not boast of having learned much, but belittle oneself by saying, "despite all I have learned I've not learned a drop in the sea of the Torah's wisdom…" And one should not act as do those who, seeing that their wisdom exceeds that of their colleagues, become prideful and take no other person into account, and are unwilling even to speak with others, thinking that they are unique in the entire world – they are surely making a great error. For our sages, of blessed memory, said that "The words of Torah are comparable to water. Just as water leaves high places for lower places, thus do the words of Torah exist only among those of humble spirit." This is the meaning of "say little and do much"; even if you have done much, meaning that you have studied Torah and fulfilled many mitzvoth, you should consider this as a minor thing so that you not be prideful among your colleagues. Which is why the verse ends with "and receive every person with a pleasant countenance" – even a person who is lesser than you.