I think most of us feel like we peaked at some point—around 25 when we were smartest, or 35 when we had most energy, or whenever we felt most alive. And we're probably right. Different things peaked at different ages.

But conflating "peak" with "best" is the trap. Your best years might not be your highest-energy years or most productive years. They might be the ones where you finally stopped proving things to yourself. Or where you got competent enough to stop being afraid. Or where you had the freedom to say no to things you hated.

Peak and best point in different directions.

What I notice in people I respect is that they stopped measuring by the thing that peaked, and started measuring by something else. The thing that got worse (looks, speed, memory) stopped being the metric. They found what actually mattered to them, not what they thought should matter. That's usually when things started getting better, even though numerically everything was declining.