Search engine optimization (SEO) is constantly changing. Search engines continuously introduce tweaks to their ranking algorithms, find new ways to rank or index website content and develop new data sources. Monitoring your visibility and traffic on a regular basis and adapting to changes where possible is key.
You’re also going to be wrong a lot of the time. That’s just how it works. For all of the powerful SEO tools out there that can help you get a sense of the competition and traffic in your vertical and what it will take to build search traffic, there will always be surprises. Accept this before you get started: you won’t always come away with success. What you will come away with, though, is more data to work from.