Cloudscape

Emotions are, for a large part and perhaps entirely, experiences which are embedded within sensations, in the form of impressions. The sensations in which emotions are imbued may be real or exist only in imagination. Thus, to better become aware how you feel, try to attribute emotions to your sensations, including sight, sound, touch, smell (and to a lesser extent, perhaps taste). When you are aware of how you feel,  to feel better, try to imagine that you fill every sensation with positive emotions.

First tell yourself how you feel, rather than denying it, and only then, say to yourself how you would like to feel, and try to feel thus. Many people try to do this the other way around, but in doing so only succeed in repressing their emotions.

When you feel negative psychological energy, do not try to stop the flow of its course, but instead divert it towards where you want, in this way transforming it into positive energy. Resisting the negative energy will only make it stronger.

If only one understands one's own feelings, one has full control over them. Actually, this is so for anything at all in the universe, but the miracle is that to control one's mind, one doesn't need to do anything in the physical world. One can tweak one's neurochemistry by using antidepressants, but it can just as well be done through sheer will.
The thing is, most people can't control their feelings because they don't understand them -- often they don't even know how they feel. The more one is aware of one's feelings, the easier it will be to harmonize them.
Often people will try to be happy and find that they fail. This is because happiness, like all higher feelings, is very complex. An emotional state isn't just one color -- it's a painting of a thousand hues; to achieve an emotional state, then, is like making a painting. Usually, one can't just be happy like that - one is happy about something. Even when it has a physical cause such as drugs, emotion always has a reason: an object. Do not try to be happy: try to enjoy.
One cannot fill one's mind with happiness without filling each sensation and each thought with happiness - for they are what compose your mind. Visualize that you were filling everything around you with energy, every sight and sound and smell and touch, and it will in turn fill you with energy -- for if all these things are encompassed in one's brain, they are part of your being.