He chooses to save Iris from the Mirrorverse but does so with computer-like logic that harms his friends and causes Iris to suffer a seizure.
Seeing the damage his logic has caused provides the emotional "shock" needed to break the Speed Force's hold and return his feelings. Other Shows with this Episode Title [S7E2] Shock to the System
Barry gains the ability of "speed-thinking" thanks to the Artificial Speed Force, but it begins to strip away his humanity, making him cold and calculating. He chooses to save Iris from the Mirrorverse
Meredith continues to hide her pregnancy and subsequent miscarriage from Derek as she struggles to get cleared for surgery. She eventually breaks her silence when she realizes she can't handle his reckless driving anymore. Meredith continues to hide her pregnancy and subsequent
In this emotional aftermath of the hospital shooting, the doctors struggle to return to "normal."
"Grey's Anatomy" Shock to the System (TV Episode 2010) - IMDb