Did the company fundamentals changed? The stock market is doing what it is suppose to do, up and down.  You however, need to stand fast for as long as your believe remains the same. Don't be discouraged by the current dip.
$Palantir (PLTR.US)$

Spare yourself from the pain of short term price movements. Do the necessary fundamental analysis on the company, put your money in and look forward to at least 3 to 5 years.
$Tesla (TSLA.US)$