The truth is, unless you are a long holder, it's quite impossible to hold Bitcoin for 10 or 20 years. Usually when we buy Bitcoin, probably we might sell when it's become double. I believe most people will do that, though we regret it later. But who knows the future? We are witnesses of huge dumps and bears as well. But if we have patience, then definitely we can sell at ATH. If we are traders, then we shouldn't regret it at all, because trading is a kind of business. Holding means you have to hold longer till it does hit your expected price.

However, I regret sometimes a few months ago when I bought a Bitcoin around $25K and sold it for $27K. But again, I think I have been using these funds for trading. Buying different coins and selling when I have profits. It's true Bitcoin is still cheap if you think about what would happen after 10 years. If you are willing to hold, I would prefer to follow the DCA strategy and just accumulate in every dump. So you will not regret it later; just consider you are depositing something for your future.