I've been taking MDMA for few years already, but I always make quite long pauses between it and take it only from a trusted source, tested as well. I always take amount for my body weight, never more. But still, I had some serotonin problems few months ago, it was out of balance. Couldn't say if it's because of MDMA. But I can't say I feel any different or weird because of it. I've tried speed for parties, but that was a big NO NO, psychedelics is not my thing as well, so I just stick with MDMA as I never had bad trips, bad experiences when on it/after it. You should always remember that all drugs must be consumed carefully and understand that it might affect your brain or body. Just MIGHT. Nothing is 100 percent safe.