There are safer ways to hold into btc's ,it's clear that some people generated thousands if not millions of wallets and are using bots with bruteforce to break any weak passwords. To have a somehow moderate wallet you might need to enter a semi-impossible to imagine word with letters/number/signs etc... making it hard for you to remember. Paper wallets might be more useful.
Perhaps not using words would be prudent as lists exist which have fancy titles like DICTIONARY etc
Skynet's new 12nm ASIC chip is able to learn at a geometric rate and can crack passwords at 500T/flop/s whilemining / coordinating missile strikes under WIN7/Ubuntu. Also it is self-conscious.
Fancy computers can quite easily hack passwords so beware!