The slaves knew it was coming, too. Booker T. Washington talks about it in Up From Slavery. After the Emancipation Proclamation is read to his family and fellow slaves, he describes the scene:
"For some minutes there was great rejoicing, and thanksgiving, and wild scenes of ecstasy [...] The wild rejoicing on the part of the emancipated coloured people lasted but for a brief period, for I noticed that by the time they returned to their cabins there was a change in their feelings. The great responsibility of being free, of having charge of themselves, of having to think and plan for themselves and their children, seemed to take possession of them. It was very much like suddenly turning a youth of ten or twelve years out into the world to provide for himself. In a few hours the great questions with which the Anglo-Saxon race had been grappling for centuries had been thrown upon these people to be solved. These were the questions of a home, a living, the rearing of children, education, citizenship, and the establishment and support of churches. Was it any wonder that within a few hours the wild rejoicing ceased and a feeling of deep gloom seemed to pervade the slave quarters? To some it seemed that, now that they were in actual possession of it, freedom was a more serious thing than they had expected to find it."
It's an interesting and reasonably short read for anyone who wants to know more about that period of history.