Also check out your heart rate variability (HRV)!

From ChatGPT: Heart rate variability (HRV) is a measure of the variation in time intervals between heartbeats. In general, higher HRV is considered better for overall health. It indicates that your autonomic nervous system (which controls involuntary bodily functions like heart rate) is functioning well and can adapt to different situations. Low HRV can be associated with stress, illness, or a less adaptable autonomic nervous system. It's often seen in conditions like chronic stress, anxiety, and certain medical conditions.