Could it be "Morgen" instead of "Morgan"? "Morgan" is not a German word, "Morgen" is (meaning "tomorrow" or "morning", depending on context, but "tomorrow" is more likely with the context of "gestern" which means "yesterday".

Might be very hard to find the lyrics with so little to go on - the words "Morgen" and "Gestern" are quite common ...

Do you remember the artist's name?