How many ETFs should I own?

Good day, I'm interested in learning more about ETF investing and I've come across the question of how many ETFs one should own. I understand that diversification is key, but at what point does owning too many ETFs become counterproductive? How should I determine the optimal number of ETFs to hold in my portfolio, considering my risk tolerance, investment goals, and the overall market conditions? Could you please provide some guidance on this matter? Thank you.