I would never see the Moon card as negative. It is the representation of lunar, feminine energy at its most pure state. To better understand it, you may wish to look up the meaning of the moon in astrology and alchemy. It is subtle and does commonly mean there is an unrealized influencement going on. But it can be positive or negative. You mustn't read each card individually at face value but take into consideration the "mood" of the cards surrounding it to determine the tone of the card. They influence one another. Each card is like a puzzle piece, they interlock to complete the entire picture.
If I saw the tower with the sun and star cards flanking it and perhaps the three of swords below, I would read it as a tragic event involving a close relationship that had a hidden silver lining, a metaphorical light at the end of the dark tunnel. Obviously the event would have something good come out of it or may just seem bad to the querent. The point is, even the darkest of cards can be influenced by their surrounding neighbors.