SSRIs take longer than 4 days to have the desired effect—it's more like 4 to 6 weeks, and is complicated by serotonin auto-receptors up-regulating first. From http://en.wikipedia.org/wiki/SSRI#Mechanism_of_action
"SSRIs inhibit the reuptake of serotonin. As a result, the serotonin stays in the synaptic gap longer than it normally would, and may repeatedly stimulate the receptors of the recipient cell. In the short run this leads to an increase in signalling across synapses in which serotonin serves as the primary neurotransmitter. On chronic dosing, the increased occupancy of pre-synaptic serotonin receptors signals the pre-synaptic neuron to synthesize and release less serotonin. Serotonin levels within the synapse drop, then rise again, ultimately leading to down-regulation of post-synaptic serotonin receptors."
Of course, they add: "Owing to the lack of a widely accepted comprehensive theory of the biology of mood disorders, there is no widely accepted theory of how these changes lead to the mood-elevating and anti-anxiety effects of SSRIs."
My own experience was definitely a wild ride, but I've been on a steady dose for many months, for some unknown value of many—I lost track. Life could still be better, but it used to be much worse. The drug wasn't the whole solution at all, but I found it to be a useful booster, giving me the motivation to take other necessary steps.
Not sure about cocaine personally though—between caffeine and nicotine (via e-cig these days), I get plenty of addictive stimulants!