Yup, keep an eye on what your citizens are doing.
But know the definitions of workers and citizens. Workers create improvements (roads, plantations, farms, mines, cottages, etc.). Citizens work tiles within the fat cross of their city, generating hammers, commerce and food.
To gain from a cottage, it must be built by a worker, then worked by a citizen for a number of turns (what, 15, 15 and 30?) to get to maximum commerce output.