A couple of things that helped me:

1) Instead of thinking of just the worse-case scenario, I should also spend time writing down and thinking about the best-case scenarios.
2) Do something with my stress. Stress is our mind telling us something is important. If I take a practical action to take care of what I'm thinking about, my mind will start to let it go. If I sit on it, it continues to race forward. For the things that are stressing me, I take as many positive actions as I can. Even writing down a note to follow-up with someone the next day makes me feel so much better.
3) Reading this book...The Confidence Gap: https://www.amazon.com/Confidence-Gap-Guide-Overcoming-Self-Doubt/dp/1590309235
4) Seeing a counselor...made a big difference for me. If that's not comfortable for you, here is an online resource: https://courses.matttownsend.com/courses/the-fast-track-to-peace

Lastly, I think you should remember the amazing things you are doing in your life, and how much God loves you. I'm certain he is really proud of the person you have become. If you are as kind in person as you are online, you are one of His favorites (even though He has a lot of favorites). You got this!