I won't write a reply to him if I haven't tried it before. I even tried it again after seeing your quote. I was able to decrypt an
old message I sent to @ BitcoinGirl.club, months ago using my own key. And I read the message in full. So its possible.
Charles-Tim answer is not completely wrong. When you encrypt a message with a certain public key then you need the corresponding private key to encrypt it.
You were able to decrypt the message you sent because you added yourself as a recipient (as BitcoinGirl.Club said) or the software you used has
encrypt to self option enabled by default which means the message was encrypted with your own public key too.
In OP's case, we can't say if he can decrypt the message he sent without knowing if he did use his own pub key to encrypt it or not.