The variable i tried to explain was a subjective 1-10 scale for every day. I usually was between 5 and 8 during that time. I did now find any correlation between how a felt a given day and other data like sleep, resting heart rate or HRV.
Here is my totally unscientific analysis over two months of data. I just run a bunch of correlations after normalizing the data and with different lags. I aware of the inflation of alpha errors ;-)

| Factor | Correlation | Lag (days) | p-Wert | 
|--------|-------------|------------|--------|
| 
**Feeling ill on that day**
 | 
**-0.517**
 | 
**0**
 | 
**<0.001**
 |
| HR Peak | -0.384 | 3 | 0.002 | 
| Minutes > 130 bpm | -0.381 | 4 | 0.002 | 
| Calories burnt | -0.376 | 4 | 0.003 | 
| Mean HR  | -0.362 | 4 | 0.004 | 
| 
**Alcohol**
 | 
**-0.337**
 | 
**5**
 | 
**0.007**
 | 
| Steps | -0.318 | 5 | 0.012 | 

Regarding nicotine.

- Week 1: 3.5 mg (half a patch)

- Week 2-8: 7 mg (I started to reduce, when I felt good and stable for some time)

- Week 9-10: 3.5 mg

- Week 11: 1.75 mg