The limbic system governs the primal urges of sex, hunger, anger, pleasure and fear; and olfactory impulses have direct pathways to this same center of the brain.
Consequently, odors and primitive emotions have a closer association because of this link-up in the limbic system.
In one experiment, human subjects were asked to complete a frustrating task as they were exposed to an unfamiliar odor.
Later the same negative emotions associated with frustration occurred when exposed to that same odor.
Scent manufacturers make millions of dollars each year by capitalizing on this connection in their attempt to emotionally get you to buy a particular product with a favorable odor -- from soaps to perfumes.
For this exercise, purchase a bottle of already blended natural essence from your local natural food store that has an unusual or unfamiliar odor -- perhaps ambergris, civet, oak moss or myrrh.
Now take it to a party or friend's house where you're likely to experience joy, laughter or some other pleasurable experience.
At the optimal height of one of these good feelings, put a few drops of the essence on your arm and smell it frequently.
In the future, to get out of a 'down' or negative mood, whip out your essence and begin smelling it again! You should become elated very quickly.
Laugh and smile to yourself when this happens, for it enhances the effect.