They just sort of boil everything off. You get down to the core of who you are, and realize that the anxiety you feel is either completely irrelevant and useless, or based on something you absolutely have control over.
The first time I tried both of them (not at the same time, obviously) was in my late 20's. I now know that I need a reset every 5-10 years, just to take stock in who I am and what I'm doing.
It really is phenomenal, the things your brain can do with a little help.
Ayahuasca is on my list, but I haven't been brave enough to do that, yet. Apparently it's more of a visceral, base high. I'm afraid that coming that close to killing my ego would be a bit too much.
A single MDMA experience broke me out of my shell. It's hard to describe how profoundly it changed my life.
MDMA was by far the most profound personally, and has made me a happier person overall. I've never fallen back into my old ways of thinking and am much more comfortable with myself.
But the first time is the most helpful and profound - once can really be enough, though I can understand why someone would want to take it 1-2 times a year just to keep it fresh in their mind.