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.
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).
It is common for Germans to 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 them that things will (probably) turn out better than they think.