Sometimes it takes repeated failures. Sometimes it takes ONE failure, when they really loved the house.
I am of the opinion that you cannot MAKE folks do what they don't already want to do. And if they do cave to pressure, they either will bail later or be miserable and make sure everyone knows you did it. 
But you can control YOUR time and focus.
You might try a takeaway close . . . "If you're not ready, perhaps we can pick up where we left off later this year, although the market shows no signs of cooling. Still, I have some others in line behind you who are ready now, waiting for paperwork . . . "
Or just tell them it doesn't get better than this, and ask what is standing between them and an offer. Drill down until they tell you what they are afraid of.

Sometimes it takes failures, rising prices and being priced out of the market.

ON the third rejection I hit the pause button.

"What is your thought process in determining what to offer?"

"Do you really think reducing the offer for your preferences is the right thing to do?"

"What has been the outcome using this approach?"

If their response is "I don't want to overpay' to the preceding questions, my availability becomes less convenient. I must be keenly aware this buyer rejects my suggestion, ignores the tools made available and will continue to diminish all in their environment including those they will ask me to recommend later. This may be more than I'm willing to pay.

I think you should ask them how many contracts are we going to mark EPIC FAIL? Then see if you still want to participate. You're a business not a tour operator right?

When they say they'll 'sleep on it,' I assure them that the house will be gone the following day.

When it is, they then trust that they'd better listen to my advice and NEVER sleep on a hot house!

It takes losing one for most to 'get it!'

Sometimes it takes missing out on a few to really believe what we are saying. Depends on the buyer. 

You can not motivate those that are not really motivated. I have a few clients like that. They talk about buying a house for years and do nothing, so i keep in touch, but have no expectations for any soon activities. 

Some people figure it out and some don't. But pushing someone into a decision only leads to buyer's remorse and bigger problems down the road. At the end of the day, we can't motivate anyone... they have to be motivated to act.

Have to have a heart to heart...down deep where they live and help them overcome whatever considerations live there. That's what's robbing them

Paul, in our crazy escalating market, I've been telling buyers conflicting things.  First, you must love the house to want to make an offer and be committed to living in it for years to come. Second, the people who buy in January are convinced they paid to much until they see what the people who buy in February had to pay, and March....  

If they are not ready, move on. If they are afraid, help them realize their fear is hurting them. 

By setting those expectiation up front when we have our first meeting.

Paul S. Henderson, REALTOR®,CRS, - perfect timing! I just taught this class (from Buffini & Company's Peak Producers!)

Losing the first one is on the buyers - should not happen for the second one. If so, tell buyers - buy or bye!

Sometimes they have to experience pain before they get it right, but once is enough!

After a new home buyer loses out on the first couple homes in this sellers market, they get the idea pretty quick.  I try to explain the market duirng our initial visit.  Some heed my warnings, some don't.

I would have a serious conversation with them to see if I can find out what it is that is holding them back... 

Paul, Candice A. Donofrio expressed my feelings perfectly...A

Sometimes it takes failure to provide the needed motivation.

It is willingness to get the property or attitude that matters.

A few years ago in Santa Clara, CA. A home defaulted was listed for $350K all viewers wanted to low ball. It was sold for $375K first week. After spending ~$40K to fix it up today. It will go for $1.2M first day.  When the price is higher the bidding fever is on fire.  Some will pay any price to get into a house. Today, if you show slight sign of skeptism, the realtors will buy it themselves and put house back on the market selling for way more.

It depends a lot on the buyer and their learning curve and the degree to which they ENJOY rejection.

If they enjoy it too much you may want to consult your own learning curve ;-) Paul S. Henderson, REALTOR®,CRS, 

I show them a updates cma on the other properties that sold around it and what it was listed for and sold for.

Find a home they cannot live without, and sometimes with our very strong market, it does take a few failures before they get their home.  

Paul S. Henderson, REALTOR®,CRS, It would depend on their buying objective. Are you wasting your time with low ball offers? Are they just indecisive? There comes a time when you may just have to let them go.

We advise.  They decide.

Sometimes it does.

It often takes losing that home they fell in love with to move faster

If they are serious buyers they will buy . 

Start charging them for each showing, it costs you every time they waste time on indecision, let it cost them too.

 Fish or cut bait.

I tell them the facts, show them the stats and some can only learn by trial and error, many times over.

Generally speaking, yes it does take many offers being rejected. 

Great question, Paul S. Henderson, REALTOR®,CRS, and terrific answers, all-around! - Tim