This is something I've been struggling with for a few years but now I'm doing better than ever because I've worked hard on myself. Here are a few advices I can give :

• Meditate, daily. Learn how to empty your mind. Breath mindfulness is my favorite technique. Because I quickly noticed how bad my breath is, done a bit of sophrology and it's really helpful. Now everytime I feel stressed out, I just stop a few seconds to breath and everything is alright.
  
• Get away from negative and stress-inducing people.
  
• If you are into drugs, try to find the cocktail that fits you the most, and do it responsibly. Don't listen to doctors. Weed keeps me happy. Benzos got me rid of overthinking and insomnia but I wouldn't recommand it, because of the addiction. It's a shame because it works so well for anxiety, but after a few months you're just craving benzos. It still helps but I sometimes feel like shit for being a drug addict. Casual psychedelics to find answers (source of fear) and improve your spiritual life. Maybe try to find a decent shaman or do a shamanic retreat if you don't like drugs. Free your mind and your ass will follow.
  
• Be stoic. Buy Meditations by Marcus Aurelius. You'll quickly realize how amazing this book is. Everytime you are anxious or upset about somethings, the solution is within this book. He had an answer for everything. It was written 2000 years ago and yet it's still more relevant today than ever.
• Try to understand the concept of the flow. Psychology flow, eastern philosophies flow, psychedelic flow. They are more or less all related. Getting away to the flow brings anxiety and overthinking. Getting closer to the flow brings hapiness and piece of mind.
• Travel as much as you can afford to, backpacking preferably. Sometimes you just get stuck. Getting away from everything for a few weeks reset your mind.

I hope it will help you find your way.