Foolhardy is right...
I'd add to Jeff's advice to use a minimum of 15 characters for anything sensitive that you want to protect and include at least two each of words, uppercase, lowercase, numbers and special characters (some sites let you use spaces as special characters).
There are a number of reputable options for storing all your passwords securely and using one LONG passphrase to access them. Last pass, Keepass to name just two.
If you're interested, there's an excellent book called 'Perfect Passwords' which explains why passphrases are better than passwords, different techniques of building secure memorable passwords, etc.
We've just had to force change everyone's passwords at work as on testing we found a disturbing number that were cracked far too easily using dictionary attacks and brute force, someone even used Password1 !!!