Recently my almost 9 year old Dogue De Bordeaux took a turn for the worse

Nearly three weeks ago he began developing ascites (fluid build up in the abdomen).  He had shown no signs of being ill and for the first few days, other than having an increasing belly size, acted normal.
Over the period of a week the fluid build up continued to grow to the point he looked VERY pregnant.  
We took him in and got the bad news that he was in end stage multi organ failure.  After consultation with the vet (who is our long term vet and very good friend) we opted to have the fluid drained with the knowledge that it was a short term fix and would allow us to bring him home for extra love and allow us to say goodbye.  This was a true blessing for all of us, especially my kids.  Our last Dogue got ill one day and we took him to the vet where they kept him overnight for observation and he passed away.  My kids were besides themselves when we took him in that they would never see them again.

It was amazing once they drained the fluid, he was back to his old self, playing, eating like a horse and generally being the goofy guy we loved.

Our vet warned us that he would likely pass away in the very near future and if he didn't the issues would return quickly and we would need to make the decision what to do.  His recommendation was to put him down when symptoms returned and before he suffered.  This is the path we chose.

There were lots of tears in the house, but we were thankful we got some more time with him.  We actually got more than twice what they expected.  On Thursday morning the ascites was back, though he looked chubby, not pregnant like he had.  He was still eating, drinking and interacting as usual when I left for work that morning.

My wife took the puppy for a walk that afternoon, and our Dogue insisted that he go to, something that is a little out of character for him.  He's not a big fan of the puppy and he's hasn't been a big fan of long walks for a few years.

I got home about 6 and he didn't come to greet me which is unusual.  I went to check on him and his belly was huge again, though he wagged his tail and interacted normally.  
I called my wife at work and told her that we would probably need to take him in the next day (today).  
I went outside to do some yard work and my daughter came out with him and said he was standing at the door and wanted to come out with me.  Not unusual.  The unusual thing was he just laid in the grass and looked at me.  Usually he is walking around, always vigilant.  After about 20 minutes he got up and started walking down the hill to our backyard (where he usually goes to the bathroom).  After a couple of minutes my daughter came running to me and said he had laid down in the bushes and wasn't breathing well and wouldn't move.  I went to check on him and he wouldn't lift his head and had positioned himself between two bushes where he was pretty much covered.  I crawled in with him and he wasn't really responsive.  I thought he had a stroke, but he was still alive.

I had to tell my kids that he was dying and they needed to say their goodbyes.  Honestly one of the hardest things I have had to do as a parent as it just crushed them.

After about an hour I was able to get him to stand and walk back into the house.  This is about 9PM.
He was not doing well and clearly was suffering.  I called my vet at home and told him what was going on and we agreed that putting him down that night was the appropriate thing to do.

I was a wreck and felt like a failure on many levels, both to him and my kids.  It was terrible not being able to help him.

I had a talk with my kids and they actually told me that it needed done as they didn't want him to suffer.

Got up to go get a blanket for the backseat for him to lay on and he immediately got up and followed me to the truck without any prompting.
Drove to the clinic and when we got there, he didn't act like he could get up to get out of the truck.  I had to lift him and sit him down.

It was the damnedest thing, he had no strength, but as soon as he hit the ground he immediately walked to the door of the clinic (not the main entry, but two doors down from the main entry where the vets enter) and just stood there.  He had never been through this door before and it required walking an extra 100 feet past the main entry.

He walked straight to the room exam room where he proceeded to hack up a huge clump (it looked like bubbles) frothy mix of blood and fluid and then went to the corner and laid down with his head buried in the corner.

The vet started an IV and gave him the medicine.  Within about 15 seconds he was just peaceful and had crossed the rainbow bridge.

Here is my question...

I was a train wreck.  He was such an integral part of our family.  He was the first pet I have ever had to put down.
After it was all over, I had this sense of relief and peace.  No tears, no heartbreak, just peace.  
I miss him dearly.  It was so odd to walk into the house tonight and him not come to greet me.  I was lost, it's been a ritual for some many years, and it was gone.

Has anyone else ever experienced that.  Just the tranquility and peace of knowing your buddy isn't suffering?

Many times - and sorry for your loss.  

Thank you
It sucks, but I wouldn't trade anything for all of the time we got with him

It does suck but, he will always be in your heart.