I had two major panic attacks in my life in my 20s and 30s where I thought I was going to die. I think one was stress and caffeine induced, and the other from going cold turkey from weed. It was the worst feeling I've ever felt before. I thought I was having a heart attack each time and my nerves were shot for days. I would wake up every 2 hours at night, and I had trouble keeping my legs still whenever I'd sit down, always bouncing on my toes from nerves. The worst part is I never saw then coming. I'd be sitting down working on my computer or taking a bus ride home when they hit, without a single thought of anything stressful. I can't imagine what people who get panic attacks more frequently feel like. Went to the doctors for both and prescribed a low dose of xanax which didn't do shit. Don't let anyone tell you you don't get withdrawals from stopping marijuana if you smoke every day for months. It took a few days and then I had a panic attack and sleepless nights for weeks after stopping cold turkey. Quit low and slow and it'll be easier.