Question: What is this thing you call 'obligation'?

I seriously, just don't know what obligations mean when it comes to relationships. There's this girl whom I have feelings towards to, and so her me. It pretty much started out fine, talking and calling and jesting with each other.

Then it started to be me who initiates the talks and calls, and she'll go,'why didn't you call/yada yada' when I don't. And I'm already losing interest at this point, and fundamentally ignorant about what should be done next.

So, how do you see obligation when it comes to a relationship with someone else?

Jam it back in, in the dark.