I don't know why, but I haven't had a horror story with a betta, as I only got one last year. And I was researching what fish would be best for me, stumbling upon this site. I am sort of lucky, I don't have guilt but I never learned directly through the actions. I did however get two dwarf gouramis in a 5 gallon tank with a couple other fish a long time ago.
I will tell you my friend said that he was barely changing the water and feeding. He said that he didn't know how the fish were surviving. One was a betta in a 2.5 gallon. And there was a 10 gallon with 2 bala sharks and a couple other fish...