The mistake which most people made is that they invest more in the low volume coins and if the coin did not perform well, all their investment is at a risk. If these low cap coins dump, its really hard for them to recover. Low cap coins can give you good return but invest very little portion of your money in them.
True, some people are overly confident in coins with low market cap, so they often pose a very dire risk, because when dumps occur on coins that are low market cap, their asset value can be 0 in a matter of days.