First, notice that the number of activated serotonin receptors has been reduced because there is less serotonin in the synapse. This means you should be starting to feel somewhat normal again. Also, the uptake pumps are still removing serotonin from the synapse, as usual, and MAO is still doing its job breaking it down. Notice that the dopamine levels in the synapse haven't lowered as much as the serotonin. This is because dopamine replenishes itself much more quickly than serotonin. Notice also that there is a lot less serotonin in your vesicles, and this is mainly why you come down. Simply put, there's no more serotonin left to be released. The MDMA may still be around trying to make your vesicles release more, but there isn't enough there. In about four hours, Ecstasy has used up most of your serotonin.

You could take more Ecstasy at this point, which a lot of people do. However, this usually doesn't work. You can't just take more ecstasy to regain the ecstasy feeling. Why? Because the ecstasy feeling is really a "serotonin feeling" and you currently don't have enough serotonin left. (It takes time for your brain to build up more, which we will be discussing soon.) Of course, if you took a lower-than-normal dose, you may not have released most of your serotonin, in which case you may feel the effects come on again if you take more. However, you cannot keep doing this repeatedly all night long. There will come a point (sooner rather than later) when you have depleted your serotonin levels so much that taking more Ecstasy will not work.