Buyers are happy to buy bitcoins from sellers because they see chance to get profit and otherwise, sellers are happy because they either take profit by selling their bitcoins or luckily cut loss or avoid loss before a possible market crash.
Sellers are indeed joyful when they sell and make some little profits until they sell and instead of the price to fall for them to rebuy again it ended up even skyrocketing to a length that they will find it difficult to buy back since the price didn't DIP as they so wished for.
There are some experience traders that knows their ways around trading and they also know the potential of Bitcoin investment, so they invest and hold for long term even though they are into trading.
However, even for a newbie that's considering to invest on Bitcoin, it's not late or too late for them. And they should consider bitcoin as a long term investment and not a get rich quick scheme. Actually, buying low and selling high is a short term investment and a short term investor always wait for a dip before buying bitcoin after selling when made a little profits. Those that considered trading instead of investment can not hold for long and such people also become emotional when they trade and get loss. So if they also invest in Bitcoin and loss little cent from their capital they become emotional and sell at lose then trade with it
And because of this kind of Mentality, they can never achieve anything good. They get overly worried about a very small dump, and decide to stop holding, They seem to know nothing about Bitcoin, that this kind of volatility of Bitcoin is a normal thing. When the price drops for a while, they panic and sell their holdings at a loss.
So not everyone can be a Bitcoin investor, real Bitcoin investors know very well that this volatility does not always exist, Bitcoin always moves forward over time. Long-term investors never worry about market fluctuations and do not panic unnecessarily at small market drops, but rather think about buying more Bitcoin at that time. And long-term investors are the ones who benefit most of the time.