The Destination Never Comes
An agile team's journey toward high performance is just that—a journey. The team may touch high performance now and then, they may even live in a state of high performance for a while, but they have never "arrived" at high performance where the story ends. No, the story continues.
Almost assuredly, as soon as they start living in high performance, something will happen to set them back. A team member will get promoted and start micromanaging his teammates. The company will reorganize, and a new vice president will assert her will over the team's direction. Someone on the team will go on maternity leave, someone will get married and move away, and someone else will simply move on. Every time one of these things happens, team dynamics will change, and the team will take a step back from high performance.
Given this, teach the team to honor their ability to fully and quickly recover from setbacks—even to honor that above the progress they've made so far or where they currently "are" on their journey. For sure, setbacks will occur. Your expectation that they will achieve greatness together, a contagion they catch and then expect of themselves, will sustain them even when the way is rough.