To get through the trapped room safely, it is imperative that the heroes don't think about pink elephants. The sign outside helpfully informs them of exactly what they need to do to avoid the trap.

Transcript

{Luke's ship flying through the clouds of Bespin}
{Luke concentrating on flying}
{Luke flying}
R2-D2: Suppress the Force, Luke! It'll give you away.
Luke: Shhh.
{the X-wing flies through the clouds}
{X-wing flying}
{Luke in the cockpit}
R2-D2: Concentrate really hard on not using it.
Luke: I was doing fine until you just reminded me of it!