(A.K.A. when to stop selling and start receiving...)
I don't know about you, but sometimes I have already decided I want to work with someone—or buy something, or visit somewhere—and so I'm already sold. But then I get sold to even more, even when I'm already 'in'. And sometimes it puts me off and I don't buy.
Now, I appreciate that there are situations where you have to do this—for example, when you're speaking at an event or recording a video, as not the entire audience you're speaking to is sold and 'in'. But I'll bet that you've sold to someone who is already sold—possibly one-to-one. And the point here is to know where your audience is at.
Say you run an open day or a launch promotion for something... you can imagine it's already a pretty safe bet that, to some degree, the people who attend are already 'sold'—they're at least sold on you or your product or the offer you put on the invite to get them there. So you don't have to sell what you already sold them again (remind them why they are here, yes, but sell them on being there—no need). What you need to focus on now is selling the next step—what to do afterwards with you to keep them moving forwards.
No, I'm going to backtrack somewhat here as I don't ever think you can 'sell' anyone anything... you can instead let them know of the benefits and outcomes of buying and allow the sale to happen by giving them all the information they need to make a decision based on what they want.
But in the context here, please take the term 'sell' to encompass what I've just said :)
I'm convinced there is a law of diminishing selling returns.
So if you imagine a peak of interest starting with "Hmmm... interesting" and moving onto "Tell me more", then working its way up to "I think I might like to buy that" to "Sold!" then please don't keep going otherwise it could move into "Actually, I'm not sure now" and "Wow, why are they flogging this so hard? Maybe it's not so good after all", etc.
So sell when you need to, then remember to leave room to receive (and don't tip it over the edge into a "No, thanks!")
Want to talk more about this?