You’re not failing, you’re not behind, you’re just struggling right now, and it’s okay, no one is holding anything against you if you don’t feel fully prepared at 18. I’m 20 and no where near half prepared for real life, let alone fully prepared. Please don’t be so hard on yourself just because you haven’t set up the rest of your life, you still have the rest of your life to set up. So what? Take your time to get everything in order, who says you need to be ready by 18? It seems like you’re holding a standard of what life should be like at 18 that simply isn’t true. It’s time to dump that standard as it’s clearly effecting you in a bad way. I understand that this will take some time, but keep repeating to yourself; there’s no rush and there’s no pressure, you don’t need to get everything you believe should be done by now, done right this second.
I didn’t get my first job until I was 19, and I have friends who are 21 and haven’t gotten their first jobs yet. Remind yourself; no rush, no pressure. I didn’t get my driver’s license until 3 years after I was old enough to get one, and got my full license months after the day I was able to do so, many of my friends are yet to get their licenses just because they feel like they don’t need to right now. Again; no rush, no pressure. As for the car insurance, you can just cancel the insurance plan as you’re not going to be driving until you get your license, and then you can get the insurance whenever you’re good to go; no rush, no pressure. You don’t really even need to buy a car at this point; no rush, no pressure. You don’t need to have your life fully organized before going to university, going to university is part of the process of organizing your life, prepare for ups and downs, and be ready to self soothe during the down periods, everyone in uni goes through this; no rush, no pressure.
I suggest you look into your university’s student help centre, counselling could be helpful for you, and getting access to accommodations through student services since you have a diagnosis can help you better manage academics (this book is helpful for learning about how ADHD effects you in university). Next, you need to kill the negative voice in your head that’s saying “you’re failing”, if that voice stays too long, depression can emerge. Be empathetic to yourself, take your situation, replace you with your best friend and tell yourself what you’d tell them if they were in the exact same boat that you’re in. Hopefully you like your friends so, hopefully you’d say words of encouragement, you’d do whatever it takes to make them feel better and support them through this rough patch, show yourself that compassion. Stop saying your failing, start saying you’re figuring things out, allow yourself to take your time while figuring things out, be kind to yourself as you’d be kind to your best friend when you hit a snag, and remember to take some time to appreciate how far you’ve come. If you don’t realize how you’ve overcome every wall you’ve hit so far then you won’t be able to see yourself overcoming the next obstacle that comes.