Spent weeks building backlinks before realizing the page wasn’t even indexed

Had one of those moments recently that made me question my entire workflow. I spent several weeks working on backlinks and trying to improve the visibility of a page, only to discover later that the page wasn't even properly indexed in Google. Looking back, it feels like I focused so much on growth tactics that I skipped over one of the most basic checks. It was a frustrating lesson, but probably a useful one. I'm curious if anyone else has had a similar experience where you invested a lot of time into something, only to realize there was a much simpler issue holding everything back. What was your most painful SEO or growth mistake, and what process did you put in place afterward to stop it from happening again? Hoping to learn from other people's mistakes before I create a few more of my own.