~snip~
Thank you for this advice, I am saving money so I can trade too. But isn't this advice counters the advice of diversifying your portfolio so you can earn a profit when one coin dipped.
No, it does not counter the advice of diversifying the portfolio because to manage many coins in our portfolio isn't easy, and that will need skills to do that. It will no problem if you have those skills, but if you don't have the skill to manage too many coins, buying bitcoin as the main investment will not be a problem.
With only having bitcoin as the investment, that means we can make a profit in the future, and it is okay to have only one coin in your portfolio. Diversifying a portfolio will be good, only if you know how to manage it.
Yes, we should also know when to buy and when to sell because other thinks that the price is low so they buy but the coin is still in high so they lose a lot of value and need to wait for another price rise to get the value back. Everyone should know how to read the pattern of coin he is holding especially when he is a big coin holder and long time holder because they may lose a lot of value with a small mistake. A big lose may give you a big disappointment that might end you up giving up crypto currency and that is not a good thing because crypto community will lose another member. Each member in crypto community is important especially those responsible one.
Unfortunately, people become greedy if the price starts to rally and breaks their target price, and they will not sell at that price instead of waiting for another high price. At least, the advice for people to sell their coin, whether it's bitcoin or altcoin, is when the price can reach 2x of your bought price so that you can make a profit. But if you can accept the risk to wait for longer, you can still hold the bitcoin, but you don't have to regret if the price can't increase higher.