A big deal with those sorts of metaphors is they tend to be sappy, and sound kind of corny.
The use of your saying or metaphor, is also important. If it's quoting some already-created saying, from a literary piece or a novel, then it really doesn't matter nearly as much what it says. or if you're attempting to have a character who writes, or speaks in super cheesy sentences, for example, that works as well.
A huge thing about metaphors, is that they work, they use specific, sometimes literal terms, to describe feelings. If you write a metaphor, but it has no emotion or purpose, it's going to sound dumb, honestly.
It helps to think of related terms (even sorts of play-on-words if you can tackle that challenge!) and giving it a sense of reality, and having it actually relate-able and understandable.
The saying "I'm dancing in your heart" doesn't work as well, because, What is dancing? so if dancing has a meaning, and the person "I" is dancing in someone else's (your) heart, that would be for the other person to decide. It would make more sense to say "You are dancing in my heart" because it is talking about the other person, to whom they obviously have affection.
There's that, while the better one is "The night sky in your heart is filled with my stars". Because it is using literal terms, in relation to one another: Stars are in the night sky. The night sky is in someone else's heart. While this also pertains to another person, if "MY" stars are in someone else's heart, unless "I" am sure the other person ("You") is in love with "Me" I can not be sure to decide that.
A better option may be "The night sky in your heart has filled me with stars". This may make more sense, because metaphors are important to who they are pertaining to.
Also think: What is the purpose? What does this metaphor mean? What is the night sky in your heart? Is it love, sorrow? WHAT. DOES. IT. MEAN. That is the most important with metaphors.
Though, otherwise, it's really not a big deal. just be careful, and re-read it and it's context. Also, ask another person to review for you, ask them to be honest, because different perspectives see things in different ways.
I read a book once, which has a character who uses a metaphor that basically says: "all of life is just a giant swirling toilet with a few spots of semi-dry to land on." This sounds really, really dumb just hearing it, but what's the context? What does it mean to the person or character?
What does it mean. That's what differentiates a good metaphor from a bad metaphor.
...That and how stubborn the person reading it is.