Time is constant - it keeps moving at a consistent pace no matter what you do. So why is it so difficult to estimate it?
I've realised that I can control only what I can control. I can't control what you might do or how you might react. It explains how I can accurately dedicate 15 minutes to reading a book, or 1 hour to tackling a social media plan, but I can't predict exactly how long it will take someone else to do the same thing - I can only estimate (and usually I'm wrong).
It's tricky for sure, best I can do is overestimate and stay optimistic.