ASD (Autism Spectrum Disorder) is manageable on its own and gets easier over time if you're high functioning. Essentially, "you get used to it," though there will always be some level of emotional, cognitive, or intimate disconnect between you, other people, and maybe even society. You will understand things that most people know intuitively like how to read other's feelings and communicate effectively through understanding it intellectually first BEFORE you can process it emotionally, which can make people on the spectrum seem weird and blunt, and rather "quirky." They tend not to associate with people and go through things solo. (Also worth noting that they're not necessary more intelligent than your average person, but tend to specialize their knowledge into specific areas, so High Functioning Autistic people usually have around or slightly higher IQs than the average, low functioning having lower, but not to such an extent of extremities.)
Anxiety is a bitch, but it's a bitch most people can understand and treat effectively. Everyone is gonna know when you have a panic attack or you start hyper-ventilating, or if you run off suddenly. Think of a constant feeling of a weight on your chest and a heavy head you get the picture. It's the stress that kills you faster, and your reaction to it is more or less a secondary response to that. Luckily, this is easier amended with meds than the disorder in the paragraph above, and has a variety of techniques that can be used to calm it. You can function in day-to-day society with it, and not be as severely impacted relative to other disorders. Still, it can be the shit sprinkles on a pile of crap sometimes if you're really stressed out about a big project or managing a lot of different things.
Major Depressive Disorder is the to live with for prolonged periods of time. It's just a sheer lack of energy, the inability to get out of bed in the mourning. You don't want to eat because it means you'll have to get up, prepare the food, cook the food, chew the food, and swallow the food. Or you don't have the ability to leave because it feels like there's this constant hollow feeling in your body of emptiness mixed with an unbearable guilt. You know it's absurd or irrational and that you need to pull yourself out of it, but that mindset doesn't make you feel better and just makes the depression worse, which makes you feel guilty which continues the cycle. You're both frustrated at yourself and yet don't have the energy to act on it because of the constant empty sadness in your heart. The rumination especially will kill you. The long periods of nothing, staring out windows and thinking or laying in bed, unable to sleep and just thinking of all the little things you messed up, or existentialist and philosophical nightmares of what life is, what's its meaning, and what the point in anything is anymore. It's like you want to disappear. The worst part is that people are less empathetic to this than the previous two if they haven't experienced it. They'll tell you that you should just be happy, or that you should pull yourself out of it, or that you're being emo, and no amount of explaining seems to justify it without having actually experienced the guilt ridden trip of the disease in which most of your time is spent thinking or in your own little world without others. Definitely, depression is a form of hell in and of itself.
I technically have a few other lesser mental health issues, but these are the big personality disorders I have. I'm sure you get the picture. And they also influence one another. Have fun dealing with that bullshit.