Fear of leaving money on the table is what stops people from choosing a niche. If you narrow, you worry the other doors close.
You can serve more than one industry. The rule is to run them one at a time. Monday is construction outreach. Tuesday is the next sector. Each day has one audience and one message.
For each niche, write down the exact problem you saw at the start of one case, what you did, and what changed. That story is your speaking point for everyone in that industry.
Then ask whether the person you are talking to would say you are their industry. If they would not, you are still too general.
Go deeper before you go wider. A buyer who thinks you work only in their field will pay more and refer you faster.