[A] I wish I knew his address = I’m sorry I don’t know his address; I wish you could drive a car = I’m sorry you can’t drive a car; I wish he was coming with us = I’m sorry he isn’t coming with us; He wished he knew the address = He was sorry he didn’t know the address; «I wish I lived nearer my work,» he said = He said he wished he lived nearer his work. [B] I wish (that) I hadn’t spent so much money = I’m sorry I spent so much money; I wish you had written to him = I’m sorry you didn’t write to him; I wished I hadn’t spent so much money = I was sorry I had spent so much money; «I wished I had taken his advice,» she said = She (said she) wished she had taken his advice. [C] If only we knew where to look for him! ; If only she had asked someone’s advice!
[[A] wish (that) + sujeto + tiempo pasado (subjuntivo) expresa pesar en relación con una situación presente; wish puede ponerse en el pasado sin cambiar el subjuntivo; los tiempos irreales de pasado no cambian en discurso indirecto. [B] wish (that) + sujeto + pretérito pluscuamperfecto (subjuntivo) expresa pesar en relación con una situación pasada; wished puede reemplazar a wish sin cambiar el subjuntivo; en discurso indirecto estos verbos son trasladados sin cambios. [C] if only puede usarse exactamente de la misma manera. Tiene el mismo significado que wish pero es más dramático.]
A Practical English Grammar (A.J. Thomson & A.V. Martinet) 