You know how the phrase "he wears his heart on his sleeve" means the guy doesn't hide his real feelings / emotions, perhaps that was more understood in the first century when they spoke "heart". Good or bad, I get this sense they didn't refrain from acting on their whims as much their Western contemporaries today. Maybe having a defined concept for "emotions" and expressing them wasn't needed then. I'm not saying they were better or worse just not as emotionally pruned as many of us are today. I'm not saying either that this is true because I wasn't there to know but if it is we might look at Bible passages a bit differently.
Even though this one's from the Old Testament, could have been a passage commonly known and given context to the word "heart" when Jesus talked about it.
26 A new heart also will I give you, and a new spirit will I put within you: and I will take away the stony heart out of your flesh, and I will give you an heart of flesh.
Ezekiel (KJV)
A stone heart describes a staunch, rigid, little to no empathy, seething with anger type of guy. But that's a modern interpretation, maybe back then they just didn't seethe as much but acted on the whims of their angered emotions more (which isn't necessarily feeling it).
So we might read this one a bit differently
35 A good man out of the good treasure of the heart bringeth forth good things: and an evil man out of the evil treasure bringeth forth evil things.
Matthew 12:35 (KJV)
If they were already expressive of their hearts, makes sense Jesus wanted them to focus on the good or in other words expressions of their heart that brings good into their lives (sounds like him talking about the law of attraction here too). I imagine a guy who always wears his heart on his sleeve and decides not to act out and hurt others would automatically be feeling more deeply.
I suppose my point is its not that emotions weren't talked about, they seemed to be, but in a different way and with a different focus more suited to those people at that time.
Well that's just how I see it for now. Hope it helps.