I've seen this phrase in memes and on t-shirts. This is used in punk rock culture quite a bit. Referring to a person as a "sheep" is usually bad.
It's someone whose personality and opinions are swayed by others. Someone whose character isn't completely independent of influence from outside sources.
Sure, it sounds cool to say. But it doesn't actually make much sense. We're all influenced by something or someone whether we notice it or not.
Our attitude towards certain things, our feelings towards certain types of people, our overall character and who we are; it's all being constantly molded by sources outside of ourselves.
The guy with the mohawk and the Poison Idea t-shirt is a "sheep" to punk rock culture itself. The bands this dude listens to shepherd his mind and attitude.
We truly are products of our environment.
We have to consider what, or more specifically who, we want as our shepherd.
In John 10:11, Jesus refers to himself as "the good shepherd" who "lays down his life for his sheep." We can choose to have the empty, tangible things of earth as our navigator or we can choose to follow the good shepherd.
The shepherd who loves us so deeply that he would be crucified to bridge the gap between our sin-soaked souls and God's eternal, perfect majesty.
Who will be your shepherd? It's your call, sheep.