Yes i've done it. I bought a new altcoin that was very cheap then a few moments later the price went down, then I sold it immediately in the hope of not having any bigger losses. A few moments later the value came back up and higher.
Regrets always comes after but you will learn with it. Move on it's not the end, opportunities are always there. Learning those mistakes will makes you a good trader. To prevent from getting loss at crypto investment best to invest at those altcoins that has good technology and strong foundation preferably at ethereum and neo.