Well, one of the most common answers given for things like this would be to imagine your audience with a bit less clothing on. But what I prefer to do it to just imagine you are at home watching tv and giving a speech to the tv.
Dopamine is the happy surge you get when you like something. This is why drugs are abused so much, because abusers want the constant rush of satisfaction. Over time, tolerance builds up and more of a drug is required to achieve the same effects. This is why some people overdose on drugs.