Experienced this first hand.

I often challenge myself to not use internet for some random problems as practice.

One time, after practically an entire day working on some personal prject; I could not push my code to github. I attempted to look up if github is down on my phone and couldn't.

Turns out there was an outage in my area. I had spent whole day programming without internet and did not notice.

After finding out I just shut down my computer and went to bed early lmao.