A diode model can be simple and ideal, or we can add behaviors that make it closer to a real diode. To create a voltage drop, the diode automatically adjusts its internal resistance. Suppose supply V is 10V, and series resistance is 10 ohms. Then we want the diode to have 2V, and the resistor to have 8V. This fixes Ampere flow at 0.8A (=8V/10). The diode automatically adopts its internal R of 2.5 ohms (=2V/ 0.8A).
Or now suppose series resistance is 10k. As before the resistor gets 8V. Current is 0.8mA (=8V/10000). So the diode adopts its internal R of 2500 ohms (=2V/ 0.0008A).