I sometimes run to work. It usually takes me about 35 minutes at the moment, give or take a couple of minutes.
The other day it was a real struggle. I had not slept well and didn’t have much energy, and it felt as if I was crawling along, so I was expecting a 36- or 37-minute time. When I got there, I was astounded to find I had only taken 33 1/2 minutes.
Conversely, I have sometimes felt like I’m flying and going really well…and then looked at the time and seen it was 35 minutes again.
What has this got to do with software? Just this: you only know how fast you are really going if you measure. You can’t rely on how it feels.