Meditation. Therapy. Volunteer work.
The main tools... Acceptance, and forgiveness. Usually applied to one's self. Definitely was true in my case.
I use music and other forms of art. Whether they be my creation or my appreciation of what is created by others it's very useful for me. If you're avoiding substance use in any form I would utilize physical activity and a ritualistic lifestyle with flexibility. Whether it's be diet change, hobby discovery, socializing (introverted peeps acknowledged, there are non crowded spaces depending on where you live, emphasis on location and feels to those without means to get to them)
I won't deny that I use cannabis you don't have to use that to take any previous advice and if you've tried these without success I'm sorry I don't have more to offer.
Find your peace. If you can't, don't give up. Ever. I won't.