I feel so bad about killing anything (insects, mice, etc)?

I'm the same. If my cat catches a mouse or theres a mouse in the house I catch it and let it go. With incents if there little flys I try to get them out, but if that doesn't work I leave it for my parents/sisters to kill. I hate doing that, but if it doesn't go it has to be done. That's only for some incents. like flys..