Agreed. Do something really deeply and for a long time. Getting started with a tech is always easy but only through several release cycles you learn the real difficulties of programming which are making changes to an old codebase, when to refactor, training new people on the system, deciding on adding new tech. But then don't get attached to this but be willing to move to other things if they make better sense.

In summary try to develop good judgement based on real world experience.