No, don't think that way. :( Everyone goes through a learning process and every good fish owner has bad things happen to them for no reason. And there are a lot of factors that are beyond your control, like the health of the betta before you even get them. If the pet stores kept them in better conditions, they wouldn't get sick so often.
You need to do what you feel most comfortable with but I hope you don't give up too quickly. And if you do take a break from bettas, there's always a place here on the forum for you when you decide to get another one.