Crypto market is very volatile, crypto market runs on news such as government announcement, project developments, partnership etc & trends such as upcoming project news such as testnet, mainnet, fork etc. Due this trends or news prices of coins can go up or down any time depends on whether it was positive or negative, that is why research is important but first you need to set your stand are you planning to invest long term or short-term.
Read one of my post hope this will help you.
https://bitcointalk.org/index.php?topic=4436763.msg39624827#msg39624827