How does fluoxetine work to change the way i feel?

Through serotonin: Fluoxetine or Prozac (fluoxetine) is the first medication in the class known as selective-serotonin reuptake inhibitors. It increases the length of time serotonin stays in your brain. Serotonin is one of the neurotransmitters or chemical messangers in the brain that helps some people with depression, anxiety or eating disorders. It can be helpful in a few other illnesses also.

SSRI: Fluoxetine is one of a category of medications that iselectively increase serotonin levels in the brain by iinhibiting reuptake. Normally when serotonin is released between 2 nerve cells it is taken back into the cell that released it to control the effect. Ssri's prevent this to increase the effect of serotonin. Decreased serotonin in certain areas of the brain plays a role in depression.