Picture yourself as a likely-illusionary Iranian Diplomat, serving an honestly progressive government giving you an unrealistic amount of authority.
Domestically, you have a theocratic government that is rapidly falling out of favor with its young people. All you need to do to advance your country forward is to end the nuclear arms sanctions crushing your every-day Iranian (but not the Guardian Council), and you'll open the country up to further democratization. ALL you need is this deal, and you're willing to give far more than any nuclear proliferation expert imagined was possible to get it. No, you aren't expanding the discussion beyond the scope of nuclear arms; the talk of political reform, of renunciations, of making formal amends is for another conversation. This is your subtle agreement to join a world order thoroughly alien from what many of your supervisors believe in, and not at all a surrender; not even the surrender of what you know in your heart is a bad policy.
However...
...Offering that much has a tacit undertone that is all too easy to forget: If you fail to bring home this deal, you will only prove the hard-liners right, and you will absolutely NEVER have this chance again. Remember, you are offering an IMMEDIATE cessation of enrichment in exchange for vague and gradual reductions in sanctions. You need results, and you need to keep your moderates faithful. Otherwise, catastrophe will strike.
That's just what you're up against, at home.
Your negotiating partners are mostly favorable to the idea of change, however their ringleader is an aging superpower with some nasty problems. For starters, you are dealing with a country that has a record of supporting terro---Sorry, "freedom fighters," like the ones who overthrew the government of Mohammad Mosaddegh, the last truly Democratic government of Iran. They do this even today, and even when you're working towards the same ends against ISIS there's a nasty taste left in your mouth. They're a continent away! What the hell are they doing in your back yard?
They have atomic bombs, but forbid others from having them. That's okay with you, because atomic bombs are horrifying weapons, but they -do- provide a certain security. North Korea gets away with crimes against humanity by having them. Meanwhile, countries like Ukraine were guaranteed protection by your negotiating partners...And when push came to shove, your negotiating partners stood by and let them be crushed. Had they kept their nuclear arms, that would never have happened. Your Syrian ally was forced under the threat of violence to surrender his own forbidden weapons, weapons of the same type that your negotiating partner silently allowed to be used against you by their Iraqi allies in the 1980's. In the early 2000's, Iraq was invaded under completely false pretenses after adhering to the very same terms that your negotiating partner is now asking you to adhere to.
Worse: The people across the table have the same problems as you do, and you know it. They have their own hardliners at home, and these lunatics have publicly said they oppose any deal you offer, no matter how sweet. They've already threatened to overrule the deal if they up and decide they want to. They have an arcane, literally apocalyptically evangelical alliance with your arch-enemies in Israel. An Israel which, you can never forget, didn't exist until the British decided to make it exist after WWI, and was recognized by UN Fiat after WWII - an act which destroyed Palestine and which has still been left unresolved by the people you're negotiating with.
The Israeli leader is worse; within a day he's gone from "pro Palestine" to "against Palestine" and back to "pro Palestine." He has repeatedly lied about how soon you will acquire an atomic bomb. His promises have zero credibility, but he has power over the the hardliners you're negotiating with. He has atomic bombs, of course, but would happily deny you them. He has sent people to assassinate your scientists, but that's somehow par-for-the-course. It's acceptable simply because these scientists were accused - not proven, necessarily - of being associated with a "dangerous" project.
But, here you are. You have to create an offer that your country can live with. And you do. You take a look at the game theory of it all, of the mock-debates between various nuclear proliferation experts and you high-ball them. You give them more than they ask for, more than any reasonable person imagines and more than most citizens - even well informed ones - think you've given. You capitulate to the inspections, no matter how humiliating. You capitulate to demands that you cede almost all of the work you have done for peaceful purposes over the last few decades. You capitulate time and again.
And then you hear the chorus of, "NO! We want more!" You hear how suddenly you are asked to renounce terrorism (Is America? Is Israel?). You are asked to guarantee the survival of a nation which you have a, well, pretty unreasonable hatred for - but they hate you, too! And their leader? He's not being asked to put anything in writing, is he? This started as a simple exchange: Reducing your theoretical nuclear capacity for relief from international sanctions.
Do you accept these sudden and off-topic demands? Do you reject them? Do you approve or despise the deal, from your own perspective? What do you do, Mr. Ambassador of Iran?