Timothy J. Keller said this quote
“ The infallible test of spiritual integrity, Jesus says, is your private prayer life. Many people will pray when they are required by cultural or social circumstances. Those with a genuinely lived relationship with God as Father, however, will inwardly want to pray and therefore will pray even though nothing on the outside is pressing them to do so. They pursue it even during times of spiritual dryness, when there is no social or experiential payoff. ”