I am agree with you that btc price will increase once again but we don't know how much time it will take to reach again 30k. It is good to set goals from the beginning that how much profit will be good for you. Actually it was your sixth sense telling you that in this place you should take profit and wait for dip to make another entry But you fell into temptation and lost opportunity to sell at 30k.
If you were a trader, you would know that I can't do much more than that but you just trusted on holding. I will recommend everyone to learn some trading also to get more Profit in these up and down situation. if you have good fund then 50% should be used for holding using DCA while other for trading.