Quarter-Life Crises and Making Changes

Something I've been trying to figure out lately is why no one tells you how hard your 20's are. I mean, seriously, there are millions of people in the world who have already survived their 20's, yet no one seems to want to offer any kind of warning about how much your 20's really take a toll on you. 
A little over a month ago, I felt like I was at the end of my rope. My anxiety was through the roof, and I decided to go to the doctor to figure out what was happening. Panic attacks were something serious. I was in my head a lot. The self-doubt was never ending, and it was like every single part of my life stressed me out. I cried a lot by myself and fell into a mini depression because I just felt so lost. 
When I went to the doctor, he diagnosed me with ADHD, something I definitely wasn't expecting. The ironic thing is that one of the side effects of ADHD is heightened anxiety, but somehow, once I started taking Vyvanse, my anxiety seemed to lower a little bit. My theory is that I was finally told that it wasn't just me. There was something "wrong" with me that was fixable, and maybe that helped to ease my mind a bit. 
While that's all well and good, I still felt so, so lost. I was still in my head, constantly questioning all of my actions and trying to figure out if I was wasting my time in every aspect of my life. 
What's my real passion? How do I figure out how to turn that into a career? What's the end game for my job? Will I stay with the company forever?  Why am I still in Louisiana? How do I know if I'm dating the person I'm meant to be with forever? What do I need to do to be truly happy?
That's just the tip of the iceberg. I felt like life was playing a game with me and tossing so many questions in my direction. 
Recently, I made a few decisions that I believe have helped steer me in the right direction. Surely I can't be the only one in my mid-twenties feeling lost with no clue where to go from here. I don't know what my passions are. I don't know what I want to do for the rest of my life. I feel like I don't even know who I am, and I'm having such a hard time trying to figure out how the hell to figure it out. 
Again I ask, why doesn't anyone tell you how hard your 20's are?It's a freaking rollercoaster of emotions and confusion and stress.
All that said, I feel like the decisions I've made have put me in a better place. I've been feeling so happy lately because I really feel like the world is my oyster and I can do whatever I want, but at the same time, I'm freaking out because I just don't know what I want. 
Are you a 20-something? Have you ever felt like you were having a quarter-life crisis? What advice do you have for people trying to figure out their lives?