A prayer is a wish. When you want to say something, it becomes a prayer. A prayer is submission to God. It is also gratitude, and forgiveness expressed on the knees of humility. A prayer is an expression of an internal hope. Even in its unexpressed form, it remains a prayer. Like a wrapped gift not opened. A prayer is the light at the end of the tunnel. Prayer is faith. Faith in hope.
Prayer is your breath. Your every desire is your prayer. The object of prayer is often God. God is everywhere. So prayer can be said anywhere.
There comes a question - is resignation a prayer? In resignation, there is no wish, no desire. We accept our fate. We allow the superpower to exercise his power without trying to influence him. So, when you resign you become prayerless. When prayer ceases, it indicates total submission. It is the destruction of ego. In resignation, you transcend yourself from individual prayer to an universal presence. You are present in the universe, not as an individual but in the universal oneness. You have no identity, you cannot pray.
The presence of life and its ambitions, wishes, desires, and fears is the cause of prayer. When the lid of death is opened, and life ceases, all activity ceases. Here prayer does not need to express itself, it exists in its latent state carrying the baggage of its past, and enjoying the bliss of universal unity.