Self-hosting does not make your data safe.
If you don't put in place, review, *and test* backup and recovery plans,,and security measures appropriate to the risk, your data are not "safe".
Your data might be less affected by the whims of third parties, which can be valuable for sure, but don't confuse that with your data being "safe".
And I say this as someone who loves self-hosting.
Any "beginners' guide to self-hosting" which doesn't lead with, or at least focus on, security and resiliency, is getting it wrong, IMHO.