You need to exercise humility while speaking to people. Doing so can make you a much more effective speaker. Doing so can also save you from a lot of heartache: the sort of heartache that is caused by pride.
In exercising humility while speaking to people, you need to frequently remind yourself that others don’t have to listen to what you have to say. Demanding that people always listen to you is setting yourself up for heartache, as there will always be folks who have a rather low opinion of you (and that should be alright).
In exercising humility while speaking to people, you also need to frequently remind yourself that others don’t have to agree with what you have to say. So getting others to listen to what you have to say is just one step (and you should be grateful for that). But getting them to actually agree to what you have to say is another issue altogether. Thus, for instance, if your argument is that the company behind Ymail is the best IT company in the world, somebody in your audience who has had nasty www.ymail.com experiences may beg to disagree. Then humility would demand that you appreciate that his or her point of view is just as valid as yours.