Mr. Market has a couple of odd behaviors. First, he will come visit you every single day and not remember his previous visits. Second, he will be in one of two moods: ecstatic or depressed.
When he is ecstatic, he will offer to buy shares of companies you hold or sell you shares of companies you don't own for a high price.
When he is depressed, he acts just the opposite, quoting low prices for the stocks you own or are interested in.