Just to play devil's advocate (or somebody who makes their living via the financial markets), it could be a good idea to think about diversifying your holdings. I have no idea, obviously, what your investment time frame is but say, for discussion purposes, you plan to retire in 30 years.
Now look at the components of the Dow Jones Industrial Average in 1991 vs. 2020:
en.wikipedia.org
So, as the cliché goes, you should keep riding your winner trade (AAPL). But having a highly concentrated portfolio or retirement account can lead to lots of volatility, or worse.