I couldn't live without one these days. I personally use Bitwarden. I have tried most of the other manager suggested in this thread. They each their own benefits. I would recommend one of the hosted services for most people (1password, Bitwarden, not LastPass). I came to prefer Bitwarden for their combination of features and openness. I have self hosted it in the past, but these days just use their hosted service.
There are a lot of side benefits to using one besides just remembering your usernames and passwords for you too.
It lets you use catch-all emails if you have your own email domain
allows you to give services their own address to track abuse
makes you more resistant to someone taking your leaked credentials from one site and using it for another
easier spam filtering
Most password managers support random password generation
Saving things that aren't logins
Family member's SSNs and DL numbers
Credit cards
Wifi passwords
Gate codes
Sharing always up to date passwords and other secrets with people (for hosted options)