Another dumb question?

So I get that I have a private key, but I don't know how to keep it secure, or at least I'm not confident that I I'll be able to keep it secure because it's not clear to me when it's safe to use it because how do I know if an app I'm inputing it into is genuine.

So just like X, but for different reasons, nostr just seems equally unappealing as a place to invest in, because in nostr' case it seems almost inevitable that, at scale, the average user is going to loose control of their private key.

I can't square this circle and nostr will not scale imo until it resolves these fundamental usability questions for the 'regular' user.