Based upon Catechism paragraph 2732.
A lack of faith is “the most common yet most hidden temptation” in our prayer, according to the Catechism, because it isn’t as straightforward as simple disbelief. Instead, lack of faith is something more insidious and subtle, which is why we may have trouble recognizing it for what it truly is.
Do we turn to God only as a “last resort,” after all else fails? That implies that we didn’t have the faith to go to Him right away in our distress, but thought that we, or others, could handle it.
On the other hand, we can be tempted to treat God as the cosmic Being Who caters to our wishes, and arranges everything just the way we’d like. In that case, our prayer devolves into telling God what we want Him to do for us. That’s not faith in God, but presumption.
While the Lord obviously wants us to ask Him for our needs, we must do so in the humble spirit of creatures who don’t really know what’s best for us, or for our eternal destiny. True faith means that we turn our needs over to the Lord in prayer, while submitting ourselves to His will, in an attitude of radical trust in His loving providence.
Sometimes a lack of faith creeps in when we try to pray, but remember other things that we have to do. At that moment, do we resolutely remain with the Lord, and put our other action-items aside for a more appropriate time? Or do we put the Lord aside?
If we’re jumping up to help someone in urgent need who depends upon us, we are serving the Lord in that person. But otherwise, if we’re just dropping prayer to do something that could wait, we’re effectively telling the Lord that He doesn’t take priority in our lives.
We may not say it, but our actions reflect that we are prioritizing something other than God. The Catechism describes this as “the moment of truth for the heart: what is its real love?”