It seems obvious to me that what you are doing wrong is not making enough backups. I have backups in 3 different hardrives, 2 pendrives, and I even put some wallets on some floppy disk just for fun and to see if they will resist the test of time. The more places you save wallets the better.

What were you thinking to leave 50 BTC in a single place?

When did the hard drive failure happen?