Another kind of door is revealed to us in this verse; an invisible door, a tiny door that is the gateway to your heart, or perhaps a literal door to a prayer closet or a small chapel in your home which several friends of mine have. Jesus is teaching that prayer is a personal intimate relationship with His Father. Like a marriage in which some aspects of the relationship are private, so our conversations with our Father in heaven are not for show or for the approval of others. But the flip side of this privacy is that it can be ignored. Out of sight, out of mind is a common struggle for most.
My daughter, mom of six boys, recently converted a very small closet in her kitchen to a prayer room. She managed to fit a tiny desk and chair in there so she could periodically escape the cacophony of her children’s noise and needs to think and pray.