Looking forward to it

What does "I'm looking forward to it" mean?  TheFreeDictionary defines it  "To anticipate something with pleasure."  Wiktionary says "To anticipate, expect, or wait for, especially with a feeling of approval or pleasure.  Be excited or eager to." And I get that it means that, culturally.  If I say "I'm looking forward to work this weekend," it sounds like I'm saying "I'm thrilled at the prospect of spending my weekend working."

But it seems to me the phrase doesn't really hold up to the sentiment.  Forward works as a metaphor for time, backward being the past and forward being the future, I don't think it works as a metaphor for mood.  Or, if it is, every direction of mood is positive, at least within the person doing the looking:

Looking forward means excited,

Looking back means nostalgic,

Looking up means admiring,

Looking down means feeling superior,

Looking to the side doesn't really mean anything, but we do have a sidelong glance, which means sharing a mutual acknowledgement of understanding.

With looking back, though, there's plenty of additional information we can provide about mood:  it's not weird to say "Looking back with regret," or "Looking back uncomfortably."  In that sense, looking back just means acknowledging things that have happened.

If we take "Looking forward" the same way, then it just means "I agree that this thing will happen."  So when I say I'm looking forward to working this weekend, all I would mean is that they scheduled me, and I intend to show up.  Which is true.

Of course, idioms like "Look forward to" have a lot more to do with what everybody agrees to hear when you say it than with what the words add up to, so the truth is I'm not looking forward to work this weekend, though they do expect me to be there and I do intend to show up.  Which is all I was really trying to say.