The thing to bear in mind about Tuesday's deal between Iran and the P5+1 countries (the United States, Britain, France, Germany, Russia and China) is that without it Iran could get nuclear weapons in a year or so whenever it wants. It has the technologies for enriching uranium, it could make the actual bombs any time it likes (every major country knows how), and the sanctions against Iran could not get much worse than they are now.
If you don't like the current deal, and you really believe that Iran is hell-bent on getting nuclear weapons, then your only remaining option is massive airstrikes on Iran. Not even the Republican Party stalwarts in the U.S. Congress are up for committing the U.S. Air Force to that folly, and Israel without American support simply couldn't do it on its own.
Then what's left? Nothing but the deal. It doesn't guarantee that Iran can never get nuclear weapons. It does guarantee that Iran could not break the agreement without giving everybody else at least two years to respond before the weapons are operational. Sanctions would snap back into place automatically, and anybody who thinks airstrikes are a cool idea would have plenty of time to carry them out.