You know you are in the right field when you find joy and pleasure in digging deeper into a field or specialty. There is plenty of space for multiple interests, but make sure you limit yourself initially enough to attain a deep level of knowledge about your main field of choice. If you find that you are not interested in digging deeper, perhaps a related field could provide insight and motivation or innovation in the field you are in, or perhaps you could pivot into a new field that shares some of your foundational knowledge. There is always the possibility of finding a new field, which has its own benefits and consequences.
Digging deep allows you to share knowledge with peers, potentially earn more, and could lead to an innovation in your region, thanks to your effort.
How to dig deeper? Internet, old and new informative books, old and new magazines/journals/newspaper articles on the subject, masters in the field, related or non-related innovations in a different field, and your own creativity.