Keep the knife razor sharp!
While the rubber is cut with sawing like motions, the sharp edge of the knife is guided by the steel wire. This tends to dull the knife. Cutting rubber with a dull knife does not work. So teach yourself to sharpen your knife and check it regularly that it still sharp enough.
However beware of accidents! Make sure not to endanger others or yourself, plan your movement and your workspace carefully!
Have a First Aid Kit in close reach.
Search for instructions of how to sharpen knives at Google or look at the Instructable for sharpening knives
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