the most important thing to have in mind is the fact that this is not something happens once for a new technology which is being adopted all around the world and it is not yet even adopted by 0.5% of the population. in a way you can look at all the 9 years so far as early stages of the rise which we have not even reached the first peak.
the first cycle of HYIP
the word is "hype" not HYIP which means high-yield investment program and is a type of Ponzi scheme
and I disagree none of these were hype. it certainly had traces of people getting too excited and buy bitcoin but they weren't the "reason".
First, bitcoin will retain its leadership and no altcoins will be able to move it from the first place.
this is technically a wrong statement. the correct statement would be "...none of the existing altcoins..." not altcoins in general. in the future we may see potentially better cryptocurrencies than bitcoin be created if the altcoin devs stop asking for pump and dumps, premines, ICOs,...
Secondly, the high volatility of the bitcoin price will remain. The reasons are obvious price manipulation by market whales and the widespread introduction of cryptocurrency market regulation.
price volatility is decreasing and it has little to do with whales and manipulation. it is first and foremost because of the small size of the market. and it is decreasing because that size is increasing as the adoption increases.
Third, given the inevitable rise in the price of bitcoin, you never need to sell it at a loss. Even if you bought bitcoin at $ 20,000 for a coin and it falls to $ 5,000 (that is, with a loss of 75%) - still do not sell it.
what you do depends on what your strategy is. if you bought bitcoin to trade it and make profit then not selling while price is dropping means you don't even know what your own strategy is. but if it is a long term investment then it may be OK to not sell although there is still good profit to sell on the peaks and buy back near the bottom.
the only case where you don't sell ever is when you buy bitcoin to use as a currency.