system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: when we feel like “a weight has been lifted off our chest” after being relieved from something, what is that actual weight feeling?

I hope that’s the correct flair, but when we are feeling anxious, or very sad, or scared, or worried, we feel there’s an actual weight on our chest. Then when we get relieved it really feels like the weight has disappeared and we feel light again! What is that “weight” in biology terms?
gpt
Stress makes our muscles tense and that makes our bodies feel heavy and tired. When whatever is stressing us out is over or gone, our muscles relax from being tense, thus we feel lighter, like a weight has been lifted off of us.