This morning I sent "Marry Christmas, XXX" to a girl. She responded, "Thank you, you too". After a while, I sent her another message, hoping that she would respond so hopefully I could initiate a chat with her. She didn't respond.

Mistake I made: I expressed more interest in her than her in me. I intended to initiate a chat with her, before she became interested in me, this is low-value behavior. It lowered my value in her perception. I shouldn't have sent her another message unless she sent me another message first. I was not desireless, I was a little bit needy. What I should do is forget about her for some time.

Hint: "Merry Christmas" messages are so generic nowadays that people either don't respond, or respond out of sheer courtesy to them... I think this was your mistake, initiating a convo using something that is socially generating reciprocity rather than with something that would gauge her interest in YOU. Why would she become interested in you? Give her a reason to be interested first, then she will respond to your messages wholeheartedly...

If a girl is interested, something as innocuous as "have a merry christmas bb" melts her heart. Build more value on the front end.