This is a false belief.
You absolutely can, and should, make the conscious decision to be more like X in your everyday life, where X is how you behave under the influence of MDMA.
I had the same problem, and got a horrible down when the drug wore off, UNTIL I realized that what the pill actually does, is SHOW ME WHAT I'M CAPABLE OF FEELING. The very INSTANT I believed it was possible, all bad feels disappeared and I was left with an afterglow that lasted for weeks.
It's not a downside of MDMA, quite the opposite; a reflection of your own weakness, the knowledge of which helps you fix it!
The feeling of bliss should come from a successful relationship with others, not some drug.
According to here[0], you are quite correct:
Amphetamines are a class of psychostimulant drugs that are widely abused for their stimulant, euphoric, empathogenic and hallucinogenic properties. Many of these effects result from acute increases in dopamine and serotonin neurotransmission. Subsequent to these acute effects, methamphetamine and 3,4 methylenedioxymethamphetamine (MDMA) produce persistent damage to dopamine and serotonin nerve terminals. This review summarizes the numerous interdependent mechanisms including excitotoxicity, mitochondrial damage and oxidative stress that have been demonstrated to contribute to this damage. Emerging non-neuronal mechanisms by which the drugs may contribute to monoaminergic terminal damage, as well as the neuropsychiatric consequences of this terminal damage are also presented. Methamphetamine and 3,4-methylenedioxymethamphetamine (MDMA) have similar chemical structures and pharmacologic properties compared to other abused substances including cathinone (khat), as well as a relatively new class of novel synthetic amphetamines known as ‘bath salts’ that have gained popularity amongst drug abusers.