And when you pray, you must not be like the hypocrites. For they love to stand and pray in the synagogues and at the street corners, that they may be seen by others. Truly, I say to you, they have received their reward . But when you pray, go into your room and shut the door and pray to your Father who is in secret. And your Father who sees in secret will reward you. And when you pray, do not heap up empty phrases as the Gentiles do, for they think that they will be heard for their many words. Do not be like them, for your Father knows what you need before you ask him.
When you pray, are you trying to impress God. When you pray, are you trying to impress others?
The Pharisees made themselves the centre of attention when they were praying. Is that what you are trying to do? It could take two different forms. Maybe you try to create a good impression of yourself by praying eloquently, emotionally or at length. Or maybe you try to avoid creating a bad impression by just keeping your mouth shut. The same pride and self-concern motivates both the show-off and the person refusing to pray if others are present. It's not about whether we speak or not but our motivation that matters
Also, our prayer does not impress God. You do not have to try to create a good impression with God by the way you pray or the words you say ("heaping up empty phrases"). God's response to your prayer is not dependent on what you said, how you said it or how many times you said it.
Jesus likens prayer to a child talking to their father. A child approaches their father in conversation freely. Maybe it's a long conversation or maybe it's short. Maybe it's eloquent or maybe it wouldn't make much sense if it was written down. Maybe other people hear maybe they don't. The child knows that whether the father listens or not is not dependent on the form of the conversation.
It's the same with us. Our prayer does not make us acceptable before God. Jesus does.