and also nowadays there are only few that has single coin in their pocket because we knew how diversifiying is the best way to invest.
Diversifying is the best way to invest if you ever have been holding bitcoin and you're satisfied with its amount. Due to that, many diversify their assets and chooses to invest into another altcoin because they think that what they're holding right now is sufficient.
If I had 1BTC I would definitely sell when the market rises and buy bitcoins again when the market falls.
This is the best approach, don't diversify yet when the market isn't at the peak or when it's not yet satisfying for the price of it. And then when you have stacked cash already with your profit there, that's the time that you're going to wait until you buy back in some time in the future again.