Prayer involve both mental prayer and spiritual prayer.
As a young Baptist boy I would spend an hour or so praying with mental prayer, you see this is just with your known words alone and I would leave that place with my spirit not able to express all that it needed to say.

When I got filled of the holy Spirit,I could pray with all of my spirit expressing it’s self
God wants us to pray both way but pray more in the spirit.

Many years ago,I gathered few folks to pray for a gentleman in an intensive care unit,we prayed the first day without any results,I asked them to come back the next day for prayers.we did same the next and no results, suddenly I asked the holy Spirit you ain’t taking hold of me and he said stop praying for the man will surely die and I stood up gave thanks and we we went home and he died later.

In as such as we believe in praying and intercession we need to understand the help of the spirit in prayers.
For the spirit helpeth our infirmity, for we know not what to pray, but many Christian think or put the reverse now for I helpeth the spirit for I know what to pray and when they pray, they pray and miss.

We know not how to pray !