The sign that the Holy Ghost is in us is that we realise, not that we are full, but that we are empty, there is a sense of absolute need.

We cannot find Him unless we know we need Him. We forget this need when we take a self-sufficient pleasure in our own good works. The poor and helpless are the first to find Him, Who came to seek and to save that which was lost.

The prerequisite for receiving the grace of God is to know you need it.