Stress affects sleep by keeping your body and mind in an alert state when they should be winding down. That can make it harder to fall asleep, easier to wake during the night, and more likely that you wake feeling unrefreshed. The relationship also runs both ways: poor sleep tends to make the next day's stress feel heavier. If you've lain awake replaying a conversation or running through tomorrow's to-do list, you already know how this feels. The good news is that the pattern is well understood, and there are practical, low-risk habits that may help. Key Takeaways Stress activates the body's alert systems, which can interfere with falling asleep and staying asleep. Stress and poor sleep can feed each other, so the cycle is worth interrupting from both sides. A consistent routine, a wind-down period, and a "worry dump" before bed are simple places to start. Caffeine, alcohol and late-night screens can make a stressed mind's sleep worse, even when th...