imo the take-away is if a president threatend another country with retaliation if their aggressive behavior continues, he/she damn well better be prepared to follow through - if not, as we see the aggressive behavior continues. Needless to say, it's wise for a president to keep his/her mouth shut and work through diplomatic channels but again, when a president shoots his/her mouth off and doesn't follow through everyone catches on quickly - witness Trump's empty threats to NK, and to a lesser extent Venezuela.
I am pleased Trump didn't pull the trigger on Iran and instead pulled away from his own rhetoric. Did Trump learn a lesson that shooting off his mouth is not smart? Absolutely not - he knows it's what the red hats want him to do...and 2020 is right around the corner.