Como saber se tenho bitcoins perdidos ou antigos?

As a cryptocurrency enthusiast, I'm often curious about the status of my digital assets. Could you please elaborate on how one can determine if they have lost or have access to old bitcoins? I understand the volatility of the crypto market and the importance of securely storing private keys, but with the sheer number of wallets and exchanges out there, it's challenging to keep track of everything. Is there a specific tool or method that you would recommend to help me identify any lost or forgotten bitcoins?