"Si Hoy Fuera Ayer" is a bolero of pure regret. It starts with the blunt fact, "Ayer se fue" (Yesterday she left), and then admits the twist: just a day later he already missed her more than he ever imagined. The title line is a wish nobody can grant: "Si hoy fuera ayer" (If today were yesterday), "Por Dios, que no la dejo partir" (by God, I wouldn't let her go).
The chorus stacks three verbs for begging, "Le ruego, le suplico, le imploro" (I beg her, I plead with her, I implore her), which is a lovely little lesson in Spanish synonyms. Then comes the sting: "Pero es tarde ya" (But it's too late now) and "Vine a saber que la amaba cuando la perdí" (I only found out I loved her when I lost her). Grammar fans will spot si hoy fuera using the imperfect subjunctive to talk about something impossible, which is exactly the mood of the whole song.