Jesus spoke of those who "hunger and thirst after righteousness." Matt. 5:6. Genuine and from the heart, spiritual longing is a form of prayer that can't fail to be answered, because it reflects the deep desire to find God. And this desire "shall be filled," as I discovered in a way that I will never forget.
After suffering a particularly virulent strain of flu, I was still mostly confined to bed three weeks later. I had been praying earnestly, and had also asked for the help of a Christian Science practitioner, but I wasn't having the kind of healing I expected.
Finally, one night as I was praying, something different happened. I began to feel a yearning—not for healing, but to be closer to God. I had a deep desire to be purified. To be purified of what, I didn't know, but the desire burned with an intensity that awed me. Over and over—for an hour or so—I implored God to make me pure, like Him.