"themself" and "ourself" are not correct because they are plural forms and must be used always in plural: "themselves" and "ourselves". On the other hand, "yourself" is used when the subject is the singular "you", and "yourselves" is used when the person referred is "you all" (plural). Hope this makes sense
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.