It has occurred to me that words describing frames of mind seem to have a strong tendency to migrate from a neutral meaning to a coloured one. To illustrate: when I ask you to define the word "temper", chances are (unless you're into metallurgy, where the word has a specific technical meaning), you're going to think first of a state of anger or peevishness, as in a "temper tantrum" or "watch out for his temper".
Originally, it simply meant any state of mind or personality. By 1814, in Mansfield Park, Jane Austen would use it in this neutral sense, but would also mention the defects of persons who "had never been properly taught to govern their inclinations and tempers", which hints at the modern, negative connotation of the word. Today, one could still say "he has an even temper", but it would be unusual for someone to say "I never noticed her temper until today" when they meant that the person in question was generally calm or cheerful.
"Mood" hasn't gone quite so far down that road, although if you talk about someone who's "moody", or remark that someone is "in one of her moods", you're talking about someone who's sulky, sullen, gloomy or angry.
The latest passenger on this train is "attitude". When I was a girl, an attitude was as likely to be sunny as dark, optimistic as pessimistic, helpful as antagonistic. Now, however, one commonly hears utterances like "she has a lot of attitude" and "that waiter really gave me attitude". In these cases, we're talking bad attitude. I have the impression that this change happened sometime during the Seinfeld era (1989 to 1998). Perhaps there's a connection?
For the record, the only example I can think of that has migrated in the opposite direction is "humour", which originally meant one of four secretions of the body (phlegm, blood, yellow bile, black bile), which in turn governed essential tendencies of mind, spirit and body: the phlegmatic (calm), the sanguine (cheerful), the choleric (angry) and the melancholic (sad). Thus "humour" came to be synonymous first with "temperament" or "personality" (as in the 1598 play by Ben Jonson, Every Man in His Humour), and then with "temper" or "mood".
William Congreve, in his 1700 The Way of the World, uses the word three times within the first 17 lines of dialogue(!), in the sense of mood, but with a strong connection to the idea of physical disposition. For example, one character remarks that another "has some humours that would tempt the patience of a stoic."
Over time, the word has migrated mainly into positive territory, so when we mention someone's "humour" today, we probably mean their capacity to be amused or amusing.
The image above is a woodcut depicting the four humours, from the book Physiognomische Fragmente zur Beförderung der Menschenkenntnis und Menschenliebe (1775-1778) by Johann Kaspar Lavater, in the public domain, from Wikimedia Commons. Clockwise from upper left: Phlegmatic, Choleric, Melancholic, Sanguine.