I wasn't joking when I posted somewhere else and said that bettas are a sort of mental health hobby for myself. Watching them gracefully swim about, doing partial water changes, trimming the plants, hand feeding them bloodworms, are all very relaxing to me. They help me feel like I have someone that relies on me (which they do...).
My newest fish, Kamehameha, was named by my boyfriend. Being 200 miles from him after spending the last 3 years living with him, seeing him every day, it has been really hard. I feel alone a lot, but I can look at my fish and think about how he helped me name him (after a frustrating hour in the store before I finally decided which fish I wanted).
However, I don't really get sad when my fish die. I know that I did my best by them, and they got to live happy lives with me. Not that I think my fish will die any time soon... But when they do, I know that another fish can come live with me and be happy. There is happiness in that, more happiness than sadness in the death of a well cared for fish. Plus, as attached as I am to them, they are kind of accents in my little ecosystems. Just like a plant, I don't expect them to live forever. It is actually kind of more tragic when a plant dies. It could have lived such a long time (decades).
Remember that the tank your fish lives in is his or her's whole world. Ask yourself this question, and answer it honestly: would you choose to live there?