Everybody is not a target market.
A target market is an area, a business type, a business size, people with a common background, a company already buying from you, a person employed in a certain industry - I think you get the idea.
As an example when I worked for a major mortgage lender, my target market was people thinking of buying a home. I didn't do refinances or mortgage transfers and I didn't work with people who had already written an offer.
Another example is with a different mortgage lender my clients were all in the same area.
A good place to determine your target market is to look at the clients you worked with in the past. Which ones did you enjoy working with the most? Which ones could afford what you sell? Which ones had the right income level? Which ones were easiest to work with? Which ones took a lot of time? Which ones took a lot of time and still push your customer service limits? Which ones were hard to deal with?
A good way to sort your clients is use an excel spreadsheet so you can see the things they have in common and their differences.
This simple exercise will save you time and make you money.