Everyone cares about backups. But creating backups of backups of backups, or old archaic files, or temporary downloads, or massive files that are available forever on the Internet such as free software tarballs, iso files etc. is foolish. This is all to say that you need to delete files before you backup!
I hope to expand this topic at a later date (and I'm 100% positive that I already have the content in one of my other sites). Until then, refer to the top answer at this StackExchange https://unix.stackexchange.com/questions/381391/find-biggest-files-and-delete-automatically