ive seen people say don't invest more than you can afford to loose , if your investing in a coin and your concerned to the extent that you feel you will loose all your money don't invest in that coin in the first place , there are plenty of coins that give a stable enough return (even if these coins go down in value they will go back up in a short time). Another important issue is don't enter into this realm intending to get rich quick , take your time and learn and research and read a lot so you can improve your understanding of how the ecosystem works. if something sounds too good to be true then usually it is.