It seems to me to presuppose a degree of detachment which is spiritually both unhealthy and unreal. It’s as though your prayers exist ‘out there’ somewhere provided for you, already fixed in form and merely requiring you to repeat them. There is value, of course, in using already written prayers, not least in a corporate worship context. We have only to think of the Lord’s Prayer to realise that. But our personal praying needs to be grounded in relationship, not in repetition.