You receive a letter from a trading firm informing you that a given market will go up over the course of the next month. Obviously you're suspicious of falling for a scam so you ignore the letter, which actually proves to be correct in its predictions.
The next month you receive another letter from the same company stating the market will go down in the month ahead. Again you ignore it and again the prediction turns out to be correct. You receive another letter the third month, and yet another one in the fourth.