Steve's Barking; Do sanctions really work?

Iran came to the bargaining table and promised new to make the bomb ( the atomic that is) .
Now I ask (myself) did they come to the table because of sanctions or did they see a good thing when they saw it? The sanctions after all didn't stop sponsoring destabilization which was the purpose of the sanctions in the first place. Maybe the bargaining was because trade was needed by those imposing sanctions?
The U.S.has been imposing sanction on Cuba since Hector was a pup but did that change the leadership of Cuba, or the way the only island is governed? Nah, only when trade was needed was the sanctions loosened and Cuban people are better off from it.
The world has had sanctions against North Korea since it became a rogue state and what can be said of the grass eating Korea. It's just as belligerent as before, and perhaps more so as the sanctions are tightened.
What about Russia and the the sanctions the world or at least some of the world placed on it? Well it appears from my living room that they've become Cold War scary.

Well who does it appear that sanctions hurt, why the people of the countries that have sanctions against them, and the companies that want to do business with them.

We're humans for crying out load can't we figure better ways of handling aggressive  behavior