Losing a cat

I lost my cat today, he had to be put down. This cat had been with us for 10 years, we never really found out what was wrong with him. Around 2 months ago he started hiding and eating less and less, he also vomited a few times back then but that stopped. First we thought that he had probably just eaten something that made him a bit sick for a while. Then he also started showing flu-like symptoms such as sneezing and coughing. We thought it was just a cat flu. When it didn't get better, my family took him to the vet and they didn't find anything in his organs or throat, i was obviously relieved at first, the only thing they​​​​​​​​​​​​​​ found was calculus in his teeth, which he got removed and supposedly was supposed to get better. He got a little better, started eating a little more until he didn't anymore, maybe a few weeks ago, he stopped eating again, only eating this paste when forced and he'd always gag first. in his last weeks he was so skinny that you could feel all of his bones, it was actually terrifying. On friday, we decided that we'd book and appointment to put him down, we knew that no matter what the original problem was​​​​​, his liver would be damaged and we didn't think he'd recover. Today was the day we had to put him down, i didn't see him the whole day because he was hiding. I only saw him when my mom was leaving to the vet with him, i let him sniff my hand. The pain and sadness feels honestly overwhelming and i have no idea how im going to survive tomorrow when i'll have to exit my home and see people other than my family. I know he's safe now and not suffering anymore, but that just makes me think of the times when he wasn't sick yet. I don't know how i'll ever get over this, its so tiring and its only the first day. ​​​​​​​​​​​​​