You should be using a password manager. My own digital life revolves around 1Password.
1Password has long been the best password manager for macOS but it's been making ground on Windows as well. In the last week or so, the folks at Agilebits who make 1Password released an update that allows 1Password to work with Microsoft Edge in Windows 10. Major good news.
MacOS X v10.13 "High Sierra" was released today. But you might want to wait. At least one rather nasty-sounding security hole has been discovered.
UPDATE: The security hole was patched within less than a day of High Sierra's release and the installer 10.13.0 installer that most users installed never had the bug.