While this strategy sounds simple enough and everyone knows about it, there are subtle issues with this:
Buy a coin and hold like you intended but take profits when the coin shoot for the sky
You see, 'sky' has no limit. How do you define 'sky'. 2X, 3X, 10X. What is you take profit at 3X and then it goes 10X?
crypto is like a circle, there will be pumps and there will be dumps,
Its not a circle, its an inward spiral that has the possibility of teleporting to the outermost fringes depending on twitter shilling. Most of the crypto is just an arrow down. Whatever goes up, WILL come down. There is no need to pin long term hopes to any of these projects until you are actually using their product and getting involved as a "creator", thereby profiting from whatever new market this token creates.
Small investors who read about dev promises and get impressed by Medium posts and decide to get emotionally invested in a project for holding long term are just bagholders. If you buy anything without understanding the business proposition and becoming a part of it yourself, you will ultimately only end up providing support or liquidity to those smarter than you.
A much better strategy is to keep a target and get the heck out as soon as you can. As long as its not a loss, you should be happy. Only a few get lucky at the cost of a lot of other hopefuls like yourself.
What goes up must come come down like you said but are you saying a coin that goes down wont go back up again? I believe the reason why this guy or girl wrote that crypto is a circle is the ups and downs, while a coin goes up and you take profit before going down opens door to another opportunity