Not realizing sooner that networking with others and creating easy-to-consume content (blog/tweets/conference presentations) that will help other programmers an

Not realizing sooner that networking with others and creating easy-to-consume content (blog/tweets/conference presentations) that will help other programmers and raise my own visibility was vastly more important that learning new and niche programming languages for career development. Not understanding that the manager career track in my geographic region was usually paid at least 25%-50% more than software engineers. Not a huge regret, but I should have job-hopped much more frequently - I have worked at only 4 companies in those 20 years and one of those for a decade+. Institutional knowledge doesn't build resumes.