The Simulator Suddenly Acts Slow?

My simulator suddenly acts very slow: it takes about 3 seconds for a modal view to show up and cover the whole screen. When I press Command+h, you can see the whole progress of how the app shrinks to the size of the icon and fades into the icon image. The most painful thing is to delete an app in the simulator: after waiting and clicking the “Delete”, it stays in the alert view. If you reset the simulator, the app is still there, and the simulator is still slow.

I thought I corrupted the simulator by accident; it ends up surprisingly easy to “fix”: All I need to do is go to the menu, “Debug” -> “slow animation”. I must accidentally press Commend+T on the simulator, and turned on the “slow animation.”

The peaceful world comes back instantly.