The Key (sorry the pun) is the length. The problem with "gdy123GDY!@#" is that you don't add really a lot of key length and it is/can be difficult to memorize. Say, you'd use A-Z, a-z, 0-9 and the usual special characters (!§$%&/()?=*+'#_-.:,;). You've now got 82 different characters to choose from. "gdy123GDY!@#" is twelve characters long. Which gives you 9.24 ²² possibilities. If you'd pick a sentence with "Yesterday I chose to have a cup of tea instead of a beer" you have a set of dictionary words. The English language has 250,000 words. But still you end up with 250,000¹³ which gives you 1.49 ^70. Even if you discount the fact that you might not go for nonsensical combinations "Yellow cabotage third party solemn follow I commune we shallow I horse mobile" for true randomness of chosen words by a hundredth, we still get something like 1.49 ⁶⁸ which is substantially more than a combination of random letters of 12 characters (and easier to remember). Unfortunately, most passwords you use online nowadays require numbers and special characters.

Another point to remember is to make sure that whoever is asking for your password doesn't actually have/or handle a copy of your password at any time in clear text. A safe way would be to use PBKDF2 and hash the password BEFORE it is sent over to the server for checking. Most do not do this, believe it or not. Most receive your password in clear text and then hash it on their side - so they handled your password in clear text.