because you using a weak password.. that means that your password is probably one single proper word.
People who try to hack peoples accounts will often try a lot of proper words as passwords to try and guess a password, if your password can be found in a dictionary then in increases the chance of being guessed.
Examples would be
Weak password:= yellow
better:= yellow1981
beter still:= 5786yellow1981
best:= 3k6bh2!hdf%sf1
obviously the last one although most secure would be a pain to remember. a good idea to get a fairly secure password is use a easy to remember phrase and then substitute letters for numbers that look similar.
such as take the phrase
open this site!
would become as a password
0penth1ss1te!