You're happy to hear a thing, but then you hear that thing is 3 months later, you're happy and at the same time you sad.
You can see that word from Stranger Things's Season 2.
Dad: You're gonna meet with Stranger Things Cast!
Boy: Oh God, I'm so happy !
Dad: But it's 3 months later.
Boy: Halfway happy.
You're happy, at the same time you sad.
Dad: You're gonna meet Stranger Things cast!
Boy: What?! I'm so happy right now!
Dad: But you gotta wait a month.
Boy: Halfway happy.