Sometimes you can use your brute strength to rip string apart with your bare hands. More often than not it's a catastrophic failure that leave you with that weird red mark around your hands.
This neat little video shows you a quick, mostly foolproof way of cutting string with your bare hands, (mostly) pain free.
It's a trick that involve using the friction of the string itself as opposed to sheer strength. Genius.
Also worthy of note: this is pretty much a perfect instructional video. So many of these things tend to drag on, with pointless chit-chat. This does exactly what it says on the tin.
I will be trying this next time I can't be bothered looking for a pair of scissors.