I kept killing all my succulents until I was looking after a friend's house while they were out of town, and they just asked me to water them by spraying them once a week with a little bottle sprayer. I had definitely been overwatering mine
So, overwatering is actually not a matter of how much water you give them, but how often. When I water, there have been times where I've left them overnight in water (I bottom water). It's simply a matter of waiting until your plant is showing signs of dehydration, and having a fast draining soil mix
