You can't decide that whether it's the highest point or lowest but you should be having satisfactory returns instead of regretting later on.Suppose you invested in around $30k and when prices went to $50k also you have made profits so you need to decide to sell or to hold as it could go above or down after that.But when it's dipping people start panicking as if it was supposed to always rise and we can't change this.So best is to make your decisions.