it's not horrible...but if you wanted it to sound like spoken fluent english it would read: A million tomorrows shall (all) pass away, do we forget (all) the joys we have today? or something along those lines.
I think it is "Ere we forget..." See the dictionary.com definition: ere ( P ) Pronunciation Key (âr) prep. Previous to; before. conj. Rather than; before and your thread title should read: "Do these lyrics have grammatical mistakes?" or "Does this lyric have a grammatical mistake?"