Therapy Wars is a side mission in South Park: The Fractured But Whole.
Plot details follow.
After completing Ghost Reconciler, this mission will eventually become available.
To begin, meet up with Craig, Tweek, and Mr. Mackey in the school gym. Here, Mr. Mackey decides Tweek and Craig should face their "Expectations", along with many other relationship issues. You get the chance to join them.
The battle is not too hard. Eventually, it will appear that expectations will continue to overwhelm you. Only then will Tweek and Craig overcome their differences and unlock a new ultimate move.
Use this to knock out the remaining enemies. This ultimate does massive damage while also confusing each target. You can now use this Ultimate Move when controlling Tweek or Craig in battle.
You also will receive the Triumph of the Heart artifact, and both the Super Craig Character Sheet and the Wonder Tweek Character Sheet.