They're absolutely right. Here's why:
You should not be holding an amount of Bitcoin that you would be tempted to sell, no matter what the price does. Within reason, obviously. If you're holding 1.0 Bitcoin, making 30k/year and Bitcoin goes to $1,000,000, okay fine, but in general, you should have enough that when Bitcoin spikes, you're elated, but not so much that when it dives you are devastated.
There is nothing wrong with funding a wallet for spending, Lightning or Chain. Spending is not selling. I mean, in practice it's not the same thing. People who 'sell' are almost always drastically decreasing their position. Someone who is 'spending' their Bitcoin, is not usually changing the amount they hold by even a quarter of a percent. Holding is great, but have fun, and spread it around.
The main reason why you should treat Bitcoin as a
long termlifetime investment, is because the world has never seen anything like this before. So treating it like something that 'has bottomed', or 'peaked', or is in a 'bull market' or 'bear', is relegating this alien thing to a class of assets that are governed by rules that simply do not apply. It's possible that Bitcoin's true value will never be determined. We might always be in a price discovery phase. But if you are in this for the long haul, then relax, and recognize that the price on any given day almost never has anything to do with holders like you. Instead, it's determined by thousands of short-term, often meaningless factors, affecting, and caused by, people who could not care less about Bitcoin itself.
See you at the finish line.