Remember Facebook went public at $50 a share, and it went down as low as about $19 a share in 2012.
Had you bought Facebook at $50 a share and held the stocks, your investment would have tripled. More amazingly, had you bought it at $20 a share and held the stocks, the value today would have been 8 times as much as the initial investment.
Today’s 4% drop is nothing at all.