就语法来说，do在这里是强调的作用，表现一种强烈的感情

All sentences have a "polarity value" and the obvious ones are positive and negative (you add negation), although there is a third value, undefined: if you ask "Do you smoke?" that question has undefined polarity, it is not positive (you are not affirming he /she does) but it is not negative, either (you are not denying he/she does); you simply do not know and must leave polarity unspecified. In typical statements, in the absence of negation, speakers assume that polarity is positive. In other words, polarity is positive by default. So, if you say "I smoke" you need not add any mark of positive polarity. If negative polarity must be expressed, negation must be added ("I do not smoke"). So, NEGATIVE polarity is not assumed by default; it is a marked option. Similarly, if you want to leave polarity unspecified, because you do not know (You are about to produce a Yes/No question), you must mark it by means of "Subject Auxiliary Inversion" and say "Do you smoke?". That is how polarity works in positive/negative statements and questions. Normally, if polarity is positive you simply write Subject + Predicate and that's it. NOW, if, in previous context your interlocutor assumes or says "Of course, you do not smoke", then you must cancel his presupposition by calling attention to what really is the case. In such circumstances you have a means to mark even the default, POSITIVE polarity. To do that, you use the auxiliary DO where NOTHING would be expected and you say "I DÓ smoke" (= contrary to what you have assumed, I smoke). Grammarians call this device "emphasis", "emphatic positive polarity" or "contrastive positive polarity". You can do that with all MAIN VERBS, but YOU CANNOT USE EMPHATIC DO BEFORE ANY AUXILIARY VERB(S): "*I do may go", "*I do have gone", "*I do am going", "*I do have gone", "*I do have been going", etc., are ALL WRONG. There is a nice explanation in an article on my website, if you are interested.

You can do that wit ALL verbs. I remember - I do remember he remembers - he does remember we think - we do think she fights - she does fight etc....