When will it stop???

[charlie_the_tuna]

we had to put our cat down on monday. we got him when we got married and he was with us for about 14 years. my boys have known him all their lives and he was a part of this family. he left us monday morning and aside from the initial blubbering like a dam fool, i have been fighting back tears for the last two days. my family is heartbroken and this house just seems so dam empty now. we've just been walking around in a slump for two days and just going through the motions of normal life.
i carry a tremendous amout of guilt that i didnt do everything i could for him. i cant sleep, i cant eat and i'm kind of making believe i'm making it through my day.
this is the single hardest thing i've ever had to do in my life. i will carry this with me forever.
all you who have had to put a beloved pet down, how long does this last? when will we be happy again? can we ever get back to normal? why does this hurt so much? he was just a cat, right? then why cant i stop crying?