If you come in contact with some very MDMA, in crystal form, I doubt you will ever come close to anxiety while on it. I think anxiety is more caused from speed, high levels of caffeine, or MDA. Sincew most pills do not contain MDMA only, speed and MDA and especially caffeine is a common addative to make the MDMA "go further".
I have snorted pure MDMA on the peak of a confusing speed come down and mushroom trip, and it took away ALL of my worries and anxieties and let me have fun. Pure MDMA you will also find intense in its own way, never mentally intense or physically too intense. More just like just a gift of utter relaxation from the Ecstasy Gods.