The best time for buying is at low price and I think if you sell your coins with profit then you should not regret after Fluctuations in coin price because you have already taken your profit so ready to make another step instead of regret about past.
If you are in doubt about other coin then just buy bitcoin now and don't sell until you achieved your target. This time is not suitable for selling but if someone is in huge profit and he cannot hold longer then selling should be preferred. Understand the market and accept your profit but I think if someone is selling their bitcoin without waiting more so he will miss the opportunity of having huge profit in Bull season.
for me the time you buy doesn't really matters but when you sell, if you have a plan of selling when the value is higher then no matter what you spent during your purchase you are sure of making some profit because you already have a plan and you are committed to this plan not minding what the prevailing circumstances are, and then when it is convenient for you then you carryout your transactions, perhaps this is where the long term approach comes in.
I don't think the mentality of selling Bitcoin after the price increases has anything to do with long-term investment. Because the price of Bitcoin can increase a lot even within 1 year. This does not mean that you have to sell Bitcoin if the price increases within 1 year. This can never be a long-term investment strategy. The price of Bitcoin fluctuates a lot, but after a long time, its price becomes several times higher. That time should be 4 to 10 years or more. As a result, real profits can be made by investing in Bitcoin. Therefore, it is necessary to get out of this mentality of selling only when the price increases and follow the complementary approach that should be adopted to continue investing effectively for 4 to 10 years.
Selling your Bitcoin when the price increases is never a long-term investment, for me, you invested to make a quick profit, a good investor will not decide to sell his bitcoin because of the price increase, when we talk about long-term investment, it means having the mind to hold your bitcoin for a long time even when the price increases without thinking of selling it, for me, four years is too short for a long-term investment, at least 6 to 10 years is good, there are people who have been holding bitcoin for more than 6 to 7 years and have not regretted it because they trust in what they are holding and how it will benefit them in the future.
You can't say that selling your Bitcoin investment when the price increase is never a long time investment, it's not every body who sell when the price increase that is a trader chasing quick profit instead of hodling for long there are investors who has been accumulating and holding Bitcoin for years now maybe more than 10 years can decide to sell little part of their Bitcoin hodling when there is an increase in price you wouldn't call that short time because he sold when the price increase you don't know how long he has been accumulating and holding Bitcoin, it is only bad for new investors to sell when the price increase because as a new investor your biggest concern should be how you can be accumulating more Bitcoin and HODL for 4-10.