"TAYLOR LEAVING AND HUGGING ANDREA I CRY," wrote a fan on social media after capturing the sweet moment between Taylor Swift and her mom Andrea after the fourth Eras Tour show at the Rogers Centre in Toronto.

Over the course of each of her three-plus-hour Eras Tour performances, Taylor Swift transports fans from the dreamy pastel paradise of “Lover” to the sultry, starlit wonderland of “Midnights” — with stops at the forested “Folklore” cabin, the pulsing cityscape of “1989” and many more in the middle.

While there's an extreme surge of happiness for many fans who scored tickets to the concert of a lifetime, there can be intense sadness when it's over. A neurologist explains why.