German Idiom: “den Teufel an die Wand malen” – “to draw the devil on the wall” – Germans use this idiom to express that someone is being overly pessimistic or only focused on a worst-case scenario.

Commonly Germans tell the pessimist “Mal nicht gleich den Teufel an die Wand” or “Man soll nicht immer gleich den Teufel an die Wand malen” to assure him that things will be (probably) turn out better than he thinks.

Apparently this saying stems from an old superstition that drawing the devil on the wall actually summons him (i.e. brings about the worst-case scenario).