No its a very bad option. You will simply burn out the pot.
Voltage dividers are not used to reduce voltage of power supplies, only signals, since
from a power perspective they are completely inefficient.
You reduce voltage for power to a motor with PWM. Alternatively a buck converter
capable of the motor's maximum current draw could be used. 500mA is unlikely to
be adequate.
If you want a small electric motor to run 24/7 you will need either a quality brushed
motor or brushless. Cheap small electric motors wear out quite quickly.
Perhaps if you asked what you wanted to achieve you will find out a better approach -
this could be the xy problem again. http://xyproblem.info/