"Blessed are the poor in spirit for theirs is the kingdom of heaven" Matthew 5:3
In order to receive the blessing of God in our lives we need to be "poor in spirit". Being poor in spirit means recognizing we are dependant on God's mercy and grace. We can do nothing to earn God's mercy nor can we in anyway pay God back.
This attitude is seen in the life of David after he was confronted by the prophet Nathan over his affair with Bathsheba. In Psalm 51 David wrote, "You do not delight in sacrifice or I would bring it."
David realized that there was nothing he could do to make amends for his sins. No way he could make it up to God. David could have sacrificed his future relationship with Bathsheba. But there was no point, since this would not have atoned for David's sin. David, like us was dependant on God's mercy and grace which is something we can not even attempt to repay. David goes on to say, "the sacrifices of God are a broken spirit, a broken and contrite heart."
Although we probably haven't committed adultery and murder we have nonetheless committed sins which have offended God's holiness and we are dependant on His mercy and grace. Our attitude should therefore be one of "poor in spirit" that is broken and humble. Sometimes God seems slow in answering our prayers but perhaps it is because He is waiting for us to be "poor in spirit". It is the person with this attitude that God can really bless.