Managing Portfolio Concentration - How much is too much in one stock?

Hey everyone, long-time lurker, first-time poster here. I've been trying to get a handle on managing my portfolio, which has admittedly grown a bit lopsided. I've had some really good runs with a few specific tech stocks over the past year, and without realizing it, they've come to represent a significant portion of my overall holdings — one in particular, $NVDA, is now nearly 25% of my portfolio value. On one hand, I'm happy with the performance, but on the other, I'm starting to feel that unease about having 'all my eggs in one basket.'

I understand the general advice about diversification, but practically speaking, at what point do you guys start trimming or rebalancing? Is there a rule of thumb you follow for maximum concentration in a single stock, or does it vary wildly based on your conviction and risk tolerance? Just trying to figure out if I should start taking some profits or if this level of concentration is considered 'normal' for higher-conviction plays.