Mark 1:16-20 And passing along by the Sea of Galilee, he saw Simon and Andrew the brother of Simon casting a net in the sea; for they were fishermen. And Jesus said to them, "Follow me and I will make you become fishers of men." And immediately they left their nets and followed him. And going on a little farther, he saw James the son of Zeb'edee and John his brother, who were in their boat mending the nets. And immediately he called them; and they left their father Zeb'edee in the boat with the hired servants, and followed him.
When we were young, our parents took us by the hand to show us the way, they didn't want us to get lost, so they watched out for us -but it didn't take long before we didn't want to hold their hand - and once we were walking by ourselves, chances are that we got lost. Some people think its something that we never outgrow - for often we are uncertain of where we are going and how to get there - some people can get lost, even if they have a map - I can't explain why we get lost - I can explain why, when we see someone lost, why we try to give them directions, even if they don't ask for them. Its hard to see someone lost, and it is certainly not wrong to want to show them the way, but what happens if they don't know where they are going, you can't give the same directions, all you can do is tell them where the various roads go.
Faith is as simple as following Jesus, Jesus leads the way, Jesus chooses the way, and we follow. And when we are young, often we follow Jesus, as we follow our parents, because they know where they are going, and we are afraid of getting lost. While there is some of what faith is in this, it is missing enough, that if we only follow out of fear, a time may come when we stop following - for in the case of fear, we tend to outgrow our childish fears. For example, the scripture says, there is only one name given under heaven by which we must be saved - and that's Jesus. We say this, and we feel that we have shown them the way - but if there is no invitation, if there is no promise, if there is no grace and mercy - if they don't know that they are lost, and don't want to be saved - then it doesn't move them to change.
All too often we try to create faith through the law, the law shows us our sins, the law can make us afraid, the law can show us that we need a savior - but the fear that comes from the law is not faith. There are 3 parts to faith, you know something, you accept it as true, and then you rely on it. If there aren't all 3 parts, you don't have faith. For example, you can know something, but not accept it as true, therefore you will probably not want to rely on it. And you can know, and accept it as true and still not rely on it. And here is why this is a big deal:
We know the disciples left everything, and followed Jesus - we know we also ought to follow Jesus, our problem is often with the leaving everything - not that there are not some things we would gladly leave - but there are some things that given a choice between Jesus and these other things the other things are the things we follow - and strictly speaking at that point they become our gods. It is good for us to look at these things, to see them as gods, and to see that they offer no salvation - but that's still not enough to change the fear of the law into walking by faith.
You see the point of the text is not found in "and they left everything" it is rather found in this, that they accepted Jesus invitation and they followed him. They knew something about Jesus, they accepted what they knew as true, and then they relied on it - they follow Jesus in faith - and leaving everything is not really leaving anything - because when you walk by faith, Jesus is everything, and when you follow Jesus you're not leaving anything important behind.
And yet, it is the leaving everything that sticks in our minds, just as it stuck in Mark's mind - Mark will later tell the story of the rich young ruler, someone Jesus called to follow, but the young man went away sad, because he just wasn't yet ready to leave everything to follow Jesus, Jesus wasn't yet his everything, he wasn't yet ready to rely on Jesus when he could rely on riches.
The point is, that in the course of our life, we have many stories about the things we left behind, when we came to follow Jesus - and as interesting as they are, they are not really important, except to show us, and others how much more important Jesus is. If you come to know Jesus, you also need to know that you can rely on him, so that you can take that step of faith, leave your old life behind and follow him.