The first time Ender Wiggin experiences a war game in the Battle Room, he quickly picks up on something that no one else does - perspective is the key to success. He watches everyone else remain oriented to the entry hallway in the zero-gravity environment, then he does something radically different. “The enemy’s gate is down,” becomes Ender’s mantra. Without gravity to define direction, Ender is free to define direction for himself, and by doing this he finds he has an advantage over everyone else.
This was not a change that just occurred suddenly the first time he entered the Battle Room, either. When the spaceship from Earth arrives at the orbiting Battle School, Colonel Graff notices that, unlike the rest of the new recruits who continue to think of “up” and “down” relative to the ship’s position (and their position in it) when it left Earth, Ender has already oriented himself relative to the ladder out of the ship and into the artificial gravity of the space station.
In his letters to various churches, Paul never gives details about the “thorn in the flesh” that he had, but it certainly seems to have impacted his daily life. It wasn't something he wanted to have - “Three times I pleaded with the Lord to take it away from me,” he tells the Corinthians. He didn't let its continuing presence ruin his ministry, however. Seeing that God wouldn't take it away, he chose instead to change his perspective. God used Paul’s weakness to show His great power, and Paul recognized this and came to accept it.
Changing our perspective isn't something that happens automatically. It is something we have to choose to do. If we make the choice, however, to let God work through us in even the most negative of circumstances, there is no limit to our strength in his power.