Don't - its dangerous ( Majority of braking force comes from front brakes) and in many countries illegal to ride on the road without 2 operational brakes.
Likely you are using too much force and not enough control. You need to learn to feather brakes rather than jam them on, while shifting the weight back and lower.
Another possibility is you are using front brakes when you should not be - e.g. down a very steep drop. If the slope is extremely steep, you need to go in slow, roll it out while on the slope, and brake once it levels out. Using the back brake only for control can help, but avoid using the front. Again, weight back and low helps with control.
Its possible the brakes are grabbing, which does make it harder to feather them properly, but this should not put you over the bars.