This is a Public Service Announcement: If someone tells you, "Bless Your Heart" chances are they have nothing nice to say about your situation or you. This is usually used when some sincerely kind BlessYourHearters is at a loss for words.
However, most modern southerners use it to help them keep their mouth shut. So, by all means, use Bless Your Heart at your disposal. It's fun.
Here are some examples:
Mother-In-Law (not mine!) walks in to your house and says, "Wow, you haven't even had time to clean the house lately, have you?"
Just take her coat and say, "Well Bless Your Heart, thanks for noticing."
Some jackass at the gym snags the machine you totally eye-balled first, "Well, Bless Your Heart, go ahead, you need it."
This can also be flipped to defend your good nature. So, same scenario at the gym, "Yeah, you need it more than I do, Bless Your Heart." Who's going to start a fight with "Bless Your Heart"? I don't think so.
Also, on the flip side, if you're a RECIPIENT of the "Bless Your Heart". That's okay, too. Just give them the nod that they are on to you and maybe go get a nice latte and sit down to reflect. If you've been Bless Your Hearted, chances are, you deserved it.
Do not overuse the Bless Your Heart. People will be mislead to believe you're a Born Again or something, and the whole mantra will lose effect.
Go and enjoy. Let me know how it worked for ya.
That's how I roll, Bless Your Heart.
My MOM always says that if someone "Blesses Your Little Heart" in reference to your baby then your baby is probably ugly. Example: "Oh, is this your new baby? (they look in at baby's face) OH!! Bless his/her little heart!". I of course have NEVER heard this in reference to one of my kids. Neither have you Mom On The Rocks!