What's the difference between useful stress and destructive stress on your mind?

Not all stress is toxic. The difference isn't the stressor itself—it's your relationship to it and whether you can recover. Useful stress (eustress) has three qualities: it feels purposeful, you have some agency in it, and there's a clear endpoint. Training for a marathon stresses your body, but you chose it and know when it ends. Destructive stress lacks these. You didn't choose it, you can't control it, and it feels endless. A looming deadline you care about can energize. Constant uncertainty about your job security erodes you. Patanjali's Yoga Sutras repeatedly emphasize 'abhyasa'—purposeful practice with clear intention—and 'vairagya'—non-attachment to outcome. This isn't about eliminating difficulty. It's about cultivating agency and perspective. Even in hard situations, you can ask: where do I have choice? What is actually in my control? Can I set a boundary on when I'm 'off'? Your nervous system doesn't distinguish between real and imagined threats, but it does respond to your sense of agency. When you feel powerless, everything feels threatening. When you feel purposeful, even hard things feel manageable. The shift is internal first.