Short answer
With a password manager, each account can have a strong unique password without you memorizing all of them.
Why unique passwords matter
If the same password is used in several places, a leak from one service can lead to compromise of other accounts.
Master password and 2FA
Protect the password manager with a long master password and enable two-factor authentication where possible.
Autofill as protection
Autofill can help you notice fake domains, because the password manager will not fill the password on the wrong website.
Common questions
Is storing passwords in an app safe?
A reputable password manager with strong encryption is usually safer than reused passwords.
Do I still need 2FA?
Yes. Password managers and 2FA complement each other.