Limit current draw from Li-ion battery
Assuming you're looking to control the speed/torque of your motor, you're going to need a motor driver. Look into an H-bridge - you can easily build one with discrete components or buy ICs that do it for you.

Next, you're going to need a way to control the duty cycle of your motor driver. One easy and popular option is to use an MCU to send a programmable PWM to the driver, it's up to you.

Finally, you'll decide how fast you want to run your motor. If using PWM control, you're actually cycling between fully on (as if it's directly connected to the battery), and fully off for the motor. Your effective current draw (and therefore speed, torque, etc.) is the average current taking into account the duty cycle of the PWM.