Data breaches are now so common that most people have at least one email address in a leaked database. That isn't cause for panic, but it is a reason to act.
Start by running an email lookup on each address you use. Note which breaches appear and when they happened.
Change the password on any affected account, and on any other account where you reused that password.
Turn on two-factor authentication wherever it's offered, ideally with an authenticator app rather than SMS.
Be extra careful with emails that reference a service you use. Attackers often use breach data to make phishing more convincing.
Finally, consider a password manager so every account gets a unique, strong password.