I think the point that you are missing is exactly what you pointed out at the beginning of your comment. Where do we want to be in future? Me and you may not know but I think the current Iran Government (and even the one that was ousted), have and had a very good idea about what they want to be.
The path Iran was going 4 decades ago would take us to where South Korea is today (although I doubt our petroleum income would allow that) . A respectable country, with strong economy and welfare for their people. Everything about that is great but one thing: They have gained all these but lost one very important thing: Their free will in world affairs. Can you imagine one instance where US decides to do something and South Korea doesn't follow? Now you may say that it is because their interests align but I don't agree. There is no way that two country's interests (one from west and one from east) always align.
South Korea has become a wealthy audience in the worlds affairs (like Switzerland, Belgium,...). There is nothing wrong with that but it is not to Iranians' taste. Our experience during 17s, 18s, and 19s shows that being a passive player minding your own business doesn't end very well in this region. Others will ignore your sovereign, tear your territory apart, steal your wealth and etc. Iran wants a bigger share of the world income AND political affairs. And that doesn't sit well with the other big players because unlike world GDP, the political chess board is limited. More power for a player means less for the rest.
Iran's current path is that of USA's 18th century and China's 19th century. They went through everything that Iran is going through today. There will be bumps, there will be hardships. But if it survive, it will prevail as an independent world grade power that has its own say on world affairs. I'm sure there were US citizens back in the early days of their revolution that thought: All of this hardship for what? Independence my .....!
So in a nutshell, here is what makes people happy these days: All that which were supposed to be given to us 4 decades ago + maintaining our own free will in world affairs. Me and you may not enjoy the benefits of the second portion in our lifetime. But the future generations will.
You should read the opinion of those against the deal in west to understand. Here is a very good one if you are interested:
Iran Nuclear Agreement: Danger Ahead | National Review Online