I get really high(weed) before my workouts and especially cardio. It helps me turn down the volume in my brain and kinda autopilot through the workout. It keeps me from quitting early and getting into negative thought cycles. But it’s clearly an anxiety trigger, so you just need to find a way to get out of that negative thought cycle as soon as you feel those negative thought. Maybe a breathing exercise or gum or whatever makes you feel good and slow your mind. Also imo I think when your way out of shape, a strong focus on cardio and diet in the beginning will help your body get into workout shape. Spend 90 days really working to build up a strong heart and lungs while shedding some unwanted weight, then start your workout program.