First, we must note that not all slaves in the South lived under the same conditions. Some lived on large plantations with many other slaves. Others lived on small farms or in cities. Some had very harsh owners while others were owned by relatively kind people. These, differences, and many others, made it so that we cannot say that all enslaved African Americans in the South lived under the same conditions.
That said, we can say that slaves generally lived under very poor conditions both materially and psychologically. In material terms, slaves had very little. They generally lived in small, one-room cabins or huts without much furniture. They typically had only one or two sets of clothing and shoes. They were not given much food, though they were not starved since they had to be able to work. In short, we can say that slaves had as little as their owners could get away with giving them.
If anything, the psychological conditions in which slaves lived were worse than the material conditions. Slaves were, of course, property. This meant that they did not really own anything, not even themselves. It also meant that they were completely under the control of their owners. We must not underestimate how insecure this made slaves. The slaves knew, for instance, that their loved ones could be sold at any moment and they could end up never seeing a sibling, parent, spouse, or child again. Female slaves knew that their owners and other whites on their plantations could sexually abuse them with impunity. All slaves knew that they could be beaten on the whims of various white people. The slaves knew that they would almost certainly live their entire lives in these conditions and so would any children they had. This must surely have been very depressing knowledge.
In short, although not all slaves lived under exactly the same conditions, slaves generally lived lives in which they had very few material possessions and in which they had very little reason to feel hopeful about their lives.