If you are learning to draw, “100 days of drawing” is fine. “100 days of making paintings for cafés” is better.
The second sentence forces you to improve the product and find distribution at the same time. You know who should see the work. Cafés know the work is meant for them. Every bad post teaches you something before day one hundred arrives.
People worry that this narrows the market too early. Buddy, your revenue is zero. You do not have a market to narrow yet.
Build publicly because failure becomes useful. Someone can interrupt you with a better technique. A customer can tell you the thing is useless. A future collaborator can watch you become good enough to call.
Do not just announce that you are building. Build towards a person. The audience is part of the product specification.