They will be making a big mistake if they decide to buy and sell then buy bitcoin again when the price goes down. Technically for you to do that you have to time the market by buying low and selling high but that is not a good way to go if you are long term investor. Timing the market is a wrong approach, and two things can happen if you decide to do that. You might sell your bitcoin too early or worse, buy back in at a high price. Before you decide to make that kind of move consider this. What if the dip never comes the way you expect, for instance you bought thinking it is the dip, and the dip kept on dipping more and more. I've seen people lose huge money form their investment because of these practices I wouldn't want anyone to make the same mistake. I believe everyone should know why they are into bitcoin. If you want to be a trader, then go along and become one it is by choice and abide to the guidelines to be a successful trader but if you say you want to be a bitcoin investor you must as well follow the right process if not you will lose as an investor. An investor should hold their bitcoin for long term. By holding long term, you don't need to sell because you want to buy the dip, you just keep holding till your maturity date which can be 6 - 10 years. As at then you might have been wise enough to know you don't really need to sell off your bitcoin rather some portion while you keep holding and stacking more.
Some people don't understand the Bitcoin market and for you to win the market, the trend should be your friend and not randomly chasing small profit and then lose everything later. There is a pattern of trend which is uptrend and down trend. In an uptrend, what we have in the time frame candle is a continuous High-Low, this is how Bitcoin price move continuously until it makes a new all time high before it makes a correction.
When Bitcoin is in a correctional phase or bear market, the time frame candles are Lower-High in falling order most of the time and will remain like that until the market decide to change trend where there is a strong support. However, many newbies that are chasing short term profits basically knows nothing about trend of the Bitcoin market.
Basically, this are HL-LH sample of candles.
A real Bitcoin holder doesn't need all of this and what happen behind the scene of Bitcoin price. Your aim is to buy and protect it, buy more at every given opportunity and stop chasing small profit that are not sustainable in the long run. You can't enjoy Bitcoin profits trying to buy and sell swinging market, you will get burn together with the little profits you made trying to outsmart the market. Instead of struggling through all that, buy and hold with peace of mind.