If you mis-manage failover, you will destroy your data. This makes proper backup even more important.
Yep, botched failovers are bad. Of course, a botched failover between replicated DBs is no walk in the park either. In many such cases you'll still want to pull backups anyway, if there's no clear way in your domain to merge two "authoritative" databases.
In all cases where you care about your data, you must take backups. There is no substitute for that step.
Additionally, you want to periodically restore your backups and test them for validity — ideally automatically. There's a saying in the ops world, borne of bitter experience:
"Your backups are only as good as their last successful restore."
Ambiguity in online discourse is an ongoing problem. Thanks for helping resolve this occurrence without acrimony.