A cardinal rule of safe reloading is to always check everything you do. Even though you've loaded thousands of the same load before, look in the book before you start again. Even though you have one progressive dedicated to .45acp, verify the powder measure is throwing the right charge. Basically, double check every single thing you do and you'll be fine.
What happens if you don't? Yesterday I was loading small quantities of .30-06 for a new pistol barrel. Primers were to be Winchester WLR. There was a blue Winchester box of 100 primers laying on my bench, and I didn't look at it carefully other than to see "rifle" on it even though I had last been loading .338 WM. Why? Because I remembered that WLR are for standard and magnum loads. I loaded my few small lots of ammo and when cleaning up, I actually looked a the primer box which was labeled WLRM, or Winchester Large Rifle Magnum. WTF? What I "remembered" was wrong. Winchester Large Pistol are for standard and magnum loads, but there are two different rifle primers: WLR and WLRM. I probably could have used the WLRM primers as all rounds had starting loads, but the safe and smart thing was to pull them down and start over. All I lost was a little time, but it was not cool.
Moral of the story: you will fuck up if you trust yourself. Check everything, then check it again. Safe reloading is really about obsessive QC.