"Different" can mean a lot of things, from how people look, to how they act, to how their bodies work internally. Our genes affect the internal workings of our body, which can also affect how we act (for example, some people are more prone to have strong emotions, and so on). But, we aren't just our genes. Our experiences also shape us, because most fo what we "know" comes direct from what we experience. Finally, we do have some amount of choice over how we react to what our genes and experience lead us to.
Probably one of the best things I heard about the third part, choice, came from a sermon: if you look at someone who is mean or nice, or stuck in bad habits or good ones, think about the fact that at one time, they weren't like that. So, how did they get to be that way? It can start with a choice, but over time, our genes have provided a mechnicsm that makes repeating the same choice easier and easier. So if you start off in the right direction, the right thing is easier to do every time. Something to think about!