Donald Miller gives some practical insights on actions and belief in his book Blue Like Jazz:

The trouble with deep belief is that it costs something. And there is something inside me, some selfish beast of a subtle thing, that doesn't like the truth at all because it carries responsibility, and if I actually believe these things I have to do something about them….

I used to say that I believed it was important to tell people about Jesus, but I never did. [My friend] Andrew very kindly explained that if I do not introduce people to Jesus, then I don't believe Jesus is an important person. It doesn't matter what I say.