Stock market always risky ,long term always gives good returns,some good stocks use to fall and return ,How much time ur holding is important,some times it takes years to return to that level,So I will say you start booking profit once after huge rally other wise you never enjoy the profit.Incase of Zomato it boottom out 40 now near to 100 ,I will say start booking profit around 110 to 115 then some at next 130,why I am saying is look Laurus journey from carona eg Laurus 70->343->260->720->280->392 now