This coin has two sides: on the one, having different passwords for each account can help protect you from hackers. On the other, the more passwords you have, the harder it is to remember them all.
To keep this from becoming a problem you can use a program like Paloma, which provides you with a database of your login information, saving everything behind one sole secure password.
This password, or key, is protected by encryption, something that Paloma makes available to you with different algorithms that you can choose between (AES, Blowfish, ARCFour...).
Paloma also includes a small assistant that can randomly create secure passwords, which are practically impossible for anyone with sinister motives to guess or exploit.