Remaining calm is always the best thing you can do. The past has told us that most people who haven't sold their coins have made decent profits by just holding onto them.
I'd definitely by bitcoin at a drop, not sure about the top 10 though as they might suffer harder than btc and a few of them (usdc and doge) might be bad for long term holding.
Keeping calm and having absolute patience are the two advantages of investing.
A decline in the market will also be an opportunity. But be aware of the long-term overall coin market trends, and don't make emotional investments.
The top coins cannot be bought intuitively. Don't buy hype coins when the market is generally down.