Never getting a betta again

My second betta just passed away today. My first one- Bubbles has developed a little tumour on his body, and has started to fall sick. He had stopped eating.... eventually he got another one on his head too. He was pretty much lifeless....just breathing. Couldn't move, couldn't eat even if he tried...one whole month had passed , he hadn't eaten.... ultimately I couldn't see it anymore, and had to put him down. But just before passing away, I offered him one pellet, trying for one last time, and he ate it off my hand, before leaving.

I was broken for days. And I promised myself that I wouldn't get attached to my other betta- Casper. He was an intelligent and good boy, but he was distant in the beginning, which made things easy for me too. But with time, he started to get really attached to me. He wouldn't go to sleep if I don't return home, loved to listen to me talk, and would always get excited the moment he'd see me. And up until yesterday, he was playing with me... though he had started to get lethargic and sleepy. And then yesterday after water change, he looked pale. Today morning also, he was responding to me, but by afternoon, he was struggling to breathe. I put my hand before him, and for the first time ever, he came up on my hand, took one big breath, and then started sinking. He was gone. I cried and cried till I fainted. He didn't wake up. I don't know how to cope with the loss.... I feel like a bad mom. He was probably desperate in his last moments...he must have thought his mom could help, but I'm useless I guess... I am never getting a pet again. Bubbles and Casper were both good little boys, who deserved a better mom.