When lactic and semi-lactic curd coagulates, the acidity of the curd when you start draining it, and the duration of the coagulation determine the body of the cheese. Lactic curd starts sticking together at first in a uniform gel where the proteins are evenly spaces apart. That is the point at which you should drain, and the corresponding pH should be about 4.6. As the acidity builds up and more time passes, those evenly spaces caseins will clump together. They'll form clumps with a lot more space in between the clumps. The texture changes and becomes a gritty, lumpy sort of cheese instead of one that is smooth and silky.
Next time, if you want better results, age for less time, and drain earlier.
