SSRIs just flatten out serotonin activity; you don't get any depressive lows or euphoric highs, just endless monotonous zombification.
Why not raise these chemicals rather than flatten them? Yohimbine blocks the brain's "sensor" for serotonin levels, so it thinks "whoa there, we don't have much serotonin do we now!?". It then pumps up the synthesis and release of serotonin in a sustainable way that won't give you withdrawals.
The only problem with yohimbine is its annoying effect of causing release of noradrenaline/adrenaline, which causes blood pressure rises, anxiety, etc. This can be easily sorted by adding carvedilol, a mixed alpha/beta blocker used to control heart rate/blood pressure. Sounds dangerous, but when titrated up slowly, it really isn't.