The market is never stable and you will always see prices fluctuating. To answer the question from the post you quoted - simply put it is a fluke that is hard to predict. You may be forced to sell at a certain price - and then the price goes up, but sometimes you buy and the price goes down. These are unpredictable conditions - but you can make a good approach where you don't have to sell everything or don't buy all at once. Sell gradually and buy with DCA - two different situation for good purposes.

Selling gradually is done by those who believe the price will go higher - but buying with DCA is a great approach to make your average purchase price lower than buying all at once. Try to take that approach when buying or selling - at least it can give you peace of mind.