So what do you do differently now in that same situation?
Now when I lower the hammer, I place the thumb of my left hand between the hammer and slide. After the sear releases, I remove my finger from the trigger. I slowly let the hammer go down by both holding it with my right thumb and slowly sliding the other thumb out just a bit. If I happen to let the hammer slip again it will be caught by either my other thumb or the half cock notch.
The hammer will then eventually move to the half cock notch. I then have to pull the hammer back very slightly as I again pull the trigger. As it goes past the half cock notch, I again remove my finger from the trigger. I then allow the hammer to slowly go the rest of the way down while I slowly slide my thumb out of the pinch between the hammer and slide.