I really like Rowan Williams' image of prayer as a sneeze in his little book that covers the essentials of the Christian faith - "Being Christian". He writes: "Prayer .. is .. like sneezing - there comes a point when you can't not do it. The Spirit wells and surges up towards God the Father. But because of this there will be moments when, precisely because you can't help yourself, it can feel dark and unrewarding, deeply puzzling, hard to speak about."
It is interesting that so many people would admit to struggles in prayer - and yet it is through prayer that we can actively engage with God, listening as well as speaking. But, yes, it is true - sometimes we just have to pray!