When Jesus' disciples prayed in the upper room after His Ascension and before the first Christian Pentecost, they probably prayed with a sense of loss. Although Jesus had promised that He would not leave them orphaned (Jn 14:18) and that He would be with them always (Mt 28:20), Jesus' disciples couldn't understand what He meant, for the Spirit had not yet been received and the Church not yet born.
When we pray with a sense of loss, our prayer may sound the same but it is prayed on a different level. For instance, after Paul saw Sosthenes violently attacked and beaten by the Corinthians (Acts 18:17), he naturally lost any sense of security. He realized he could be killed at any moment. When he prayed "Come, Holy Spirit," he probably prayed it on a deeper level than most of us are accustomed to. I remember seeing a widow pray, "Come, Holy Spirit," a couple of hours after her husband's death. She received the Spirit as never before since she prayed for the Spirit as never before. I've seen people lose their health and lose the unity in their marriages. When these people, in their loss, pray, "Come, Holy Spirit," all heaven breaks loose.
When we think we've lost everything, we can pray for the Spirit and receive more than we can ever ask for or imagine (Eph 3:20). Come, Holy Spirit!